NEW YORK, N.Y. - More than a billion people now log into Facebook each month to check up on old friends, tag photos of new ones and post about politics, religion, cats or what their kids are doing.

That's double the 500 million it hit in July 2010 — what now seems like a lifetime but was a little more than two years ago. August 2008 marked another big juncture, 100 million users.

The latest milestone also amounts to nearly half of the world's roughly 2.5 billion Internet users, as measured by the International Telecommunications Union.

So who are these people?

Most of them — 81 per cent — live outside of the U.S. and Canada. Many of them log in on mobile devices rather than personal computers, and the company now has 600 million mobile users.

The people joining now are young, with a median age of 22. It was 23 in 2010 and 26 in 2008 and 2007. Most of them are from Brazil, India, Indonesia, Mexico and the United States. They are unlikely to be from China, the world's most populous country and home to its largest Internet population. And millions of them are not actual people. Facebook acknowledged in August that 8.7 per cent of its then-955 million users may be duplicate or false accounts. At that rate, as many as 87 million accounts are fake.

As expected, the longer users are on Facebook, the more "friends" they have on the site. A user who signed up two years ago has an average of 305 friends. Someone who signed up in December 2005, when Facebook had nearly 6 million users, now has nearly 600 friends, on average.

CEO Mark Zuckerberg marked the milestone on his Facebook page, as he has in the past when the site's users hit nice round numbers.

"If you're reading this: thank you for giving me and my little team the honour of serving you," he wrote. "Helping a billion people connect is amazing, humbling and by far the thing I am most proud of in my life."

But he acknowledged in a "Today" show interview that the company is going through a difficult patch.

"We're in a tough cycle now and that doesn't help morale, but people are focused on what they're building," he told Matt Lauer during the interview.

The Menlo Park, California-based company's stock never recovered from a botched initial public offering in May, at one point seeing its value slashed in half by shareholders who don't think it's increasing revenue fast enough, especially from its fast-growing mobile user base.

Last month Zuckerberg gave his first interview since Facebook's shaky IPO and since that time he's been working hard to boost confidence among investors, employees and the public.

The 28-year-old executive also continued to reassure that he is the right person to lead Facebook, as some on Wall Street have questioned whether he has the ability to lead a large public company.

"I take this responsibility very seriously," he said.

To further mark the occasion, Facebook also released a video Thursday that, somewhat abstractly, seeks to illustrate its ubiquity and utility in connecting people to one another. Directed by Alejandro Gonzalez Inarritu ("Babel," ''21 Grams" and "Amores Perros"), the video starts off with an empty red chair suspended in midair in a forest. Then it moves to chairs with people, first just one then two, and groups around a dinner table, dancing, playing. Then more chairs.

"Chairs. Chairs are made so that anyone can sit down and take a break. Anyone can sit on a chair," a woman's voice assures the viewer. "And if the chair is large enough, they can sit down together. And tell jokes. Or make up stories. Or just listen. Chairs are for people. And that is why chairs are like Facebook."

See also: doorbells, airplanes and bridges.

"These are things people use to get together so they can open up and connect," the ad continues. The conclusion? The universe is vast and dark and makes us wonder if we are alone. And there is Facebook. And chairs, of course.

It's Facebook's first advertising campaign surrounding its brand. So far, though, the company is not saying whether the video will air on television.

Facebook Inc.'s stock slipped a penny to $21.82 in afternoon trading. The shares are 43 per cent below their $38 IPO price.

___

AP Business Writer Michelle Chapman contributed to this story. Reach Barbara Ortutay on Twitter at https://twitter.com/BarbaraOrtutay.

Online:

The Facebook chair video: http://www.facebook.com/photo.php?v=3802752155040

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  • You Luv 'Call Me Maybe'

    Remember when you were having that <em>really bad</em> day and blasted Carly Rae Jepsen's "Call Me Maybe" 23 times on Spotfiy? Yeah... well, we witnessed that low moment via your Facebook profile's ticker, the real-time mini feed located in the upper right hand corner of Facebook pages. If you don't want to share your (possibly embarrassing) musical preferences with your Facebook friends, make sure to turn off the "Share to Facebook" button (at the top right of your Spotify desktop app).

  • You Can't Resist Clicking On Sketchy, Sexy Video Links

    Some Facebook apps, like Socialcam, are designed to make you click on content by using sleazy, eye-catching headlines. "Socialcam's 'trending' videos read like a bunch of crossovers between the 'American Pie' franchise and 'Jackass,'" <a href="http://www.washingtonpost.com/socialcams-so-sleazy-its-insightful/2012/06/05/gJQAor3FGV_story.html" target="_hplink">The Washington Post wrote</a> in June. If you're a SocialCam user, remember that the spam-like titles of videos you view automatically pop up on your profile, so your friends all might know when you've watched "CraZy ThReeSom!" or "Two Wasted Chicks" last week.

  • You Can't Get Enough Sideboob In Your News

    Glancing at a juicy article on how Miley Cyrus <a href="http://www.huffingtonpost.com/2012/05/22/miley-cyrus-side-boob-actress-sex-scenes-losing-virginity_n_1536026.html" target="_hplink">flashed some sideboob</a>? While this wouldn't phase some Facebook users, others would prefer not to have anything with the word "sideboob" published on their profiles or in friends' News Feeds. Facebook's social reader apps track the articles you read, and with permission you grant when first downloading the app, then post the stories automatically to your wall. So be weary of those scandalous headlines promising half-naked pictures.

  • How Old You Are

    Some people love getting birthday wishes via Facebook. But putting your your full date of birth on any social networking site means strangers are privy to information that can be used to steal your identity. If you want to keep your birthday up online, consider taking the safe route and nix the year.

  • You Went Out Boozin' Every Night Last Week

    Friends or apps can now tag your location via Facebook. But maybe you don't want everyone to know you're visiting that neighborhood dive bar for the fourth night this week. "There isn't a specific setting to block people from tagging you in a post that includes a location," <a href="https://www.facebook.com/help/location/privacy" target="_hplink">Facebook's site reads</a>. This means if you don't want your whereabouts known, you'll have to change your Timeline setting to approve all tags before they're posted, or manually remove the tags once they've been published.

  • You Are Addicted To Artsy Pics Of Beaches And Breakfast Food

    Photo-sharing app Instagram is relatively direct in telling you where your pictures are posted. But you might unknowingly be photo-spamming your friend's Facebook feeds by letting the app re-post every picture you "like" onto Facebook. And things could get a little dicey depending on <a href="http://www.huffingtonpost.com/2012/08/30/instagram-porn_n_1842761.html?utm_hp_ref=technology" target="_hplink">what types of images you view.</a> Luckily this feature is easy to change. Just go into the settings options on your Instagram app, click the "Share Settings" tab and turn off the setting that shares "Liked" photos to your Facebook timeline.

  • What Your Kids' Names Are

    Tagging or naming younger children on Facebook can be a dangerous move. Similar to putting your full birthday on the interent, you could be offering up too much information and enabling a breach of privacy. "If your child isn't on Facebook and someone includes his or her name in a caption, ask that person to remove the name," <a href="http://www.consumerreports.org/cro/magazine-archive/2010/june/electronics-computers/social-insecurity/7-things-to-stop-doing-on-facebook/index.htm" target="_hplink">Consumer Reports advises</a>.


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  • Your Birth Date And Place

    While it might be nice to hear from Facebook well-wishers on your birthday, you should think twice before posting your full birthday. Beth Givens, executive director of the <a href="http://www.privacyrights.org/" target="_hplink">Privacy Rights Clearinghouse</a> <a href="http://finance.yahoo.com/family-home/article/110674/6-things-you-should-never-reveal-on-facebook">advises</a> that revealing your exact birthday and your place of birth is like handing over your financial security to thieves. Furthermore, Carnegie Mellon researchers recently <a href="http://arstechnica.com/tech-policy/news/2009/07/social-insecurity-numbers-open-to-hacking.ars" target="_hplink">discovered</a> that they could reconstruct social security numbers using an individual's birthday and place of birth. Rather than remove your birthday entirely, you could enter a date that's just a few days off from your real birthday.

  • Your Mother's Maiden Name

    "Your mother’s maiden name is an especially valuable bit of information, not least since it’s often the answer to security questions on many sites," writes the <em><a href="http://bucks.blogs.nytimes.com/2010/10/12/what-not-to-tell-facebook-friends/?src=tptw" target="_hplink">New York Times</a></em>. Credit card companies, your wireless service provider, and numerous other firms frequently rely on this tidbit to protect your personal information.

  • Your Home Address

    Publicizing your home address enables everyone and anyone with whom you've shared that information to see where you live, from exes to employers. Opening up in this way could have negative repercussions: for example, there have been instances in which <a href="http://www.huffingtonpost.com/2010/02/17/please-rob-me-site-tells_n_465966.html" target="_hplink">burglars have used Facebook to target users</a> who said they were not at home.

  • Your Long Trips Away From Home

    Don't post status updates that mention when you will be away from home, <a href="http://bucks.blogs.nytimes.com/2010/09/15/dont-tell-facebook-friends-that-youre-going-away/" target="_hplink">advises</a> <em>New York Times</em> columnist Ron Lieber. When you broadcast your vacation dates, you might be telling untrustworthy Facebook "friends" that your house is empty and unwatched. "[R]emind 'friends' that you have an alarm or a guard dog," Lieber writes.

  • Your Short Trips Away From Home

    Although new features like Facebook Places encourage you to check in during outings and broadcast your location (be it at a restaurant, park, or store), you might think twice even before sharing information about shorter departures from your home. "Don’t post messages such as 'out for a run' or 'at the mall shopping for my sweetie,'" Identity Theft 911 <a href="http://identitytheft911.com/company/press/release.ext?sp=11132" target="_hplink">cautions</a>. "Thieves could use that information to physically break in your house."

  • Your Inappropriate Photos

    By now, nearly everyone knows that racy, illicit, or otherwise incriminating photos posted on Facebook can cost you a job (or worse). But even deleted photos could come back to haunt you. Ars Technica recently <a href="http://arstechnica.com/web/news/2010/10/facebook-may-be-making-strides.ars" target="_hplink">discovered</a> that Facebook's servers can store deleted photos for an unspecified amount of time. "It's possible," a Facebook spokesperson <a href="http://arstechnica.com/web/news/2010/10/facebook-may-be-making-strides.ars" target="_hplink">told</a> Ars Technica, "that someone who previously had access to a photo and saved the direct URL from our content delivery network partner could still access the photo."

  • Confessionals

    Flubbing on your tax returns? Can't stand your boss? Pulled a 'dine and dash?' Don't tell Facebook. The site's privacy settings allow you to control with whom you share certain information--for example, you can create a Group that consists only of your closest friends--but, once posted, it can be hard to erase proof of your illicit or illegal activities, and difficult to keep it from spreading. There are countless examples of workers getting the axe for oversharing on Facebook, as well as many instances in which <a href="http://www.huffingtonpost.com/2010/08/16/arrested-over-facebook-po_n_683160.html" target="_hplink">people have been arrested</a> for information they shared on the social networking site. (Click <a href="http://www.huffingtonpost.com/2010/07/26/fired-over-facebook-posts_n_659170.html" target="_hplink">here</a> to see a few examples of Facebook posts that got people canned.)

  • Your Phone Number

    Watch where you post your phone number. Include it in your profile and, depending on your privacy settings, even your most distant Facebook "friends" (think exes, elementary school contacts, friends-of-friends) might be able to access it and give you a ring. Sharing it with Facebook Pages can also get you in trouble. Developer Tom Scott created an app called <a href="http://www.huffingtonpost.com/2010/05/24/evil-facebook-app-exposes_n_587144.html" target="_hplink">Evil</a> that displays phone numbers published anywhere on Facebook. <a href="http://www.huffingtonpost.com/2010/05/24/evil-facebook-app-exposes_n_587144.html" target="_hplink">According to Scott</a>, "There are uncountable numbers of groups on Facebook called 'lost my phone!!!!! need ur numbers!!!!!' [...] Most of them are marked as 'public', and a lot of folks don't understand what that means in Facebook's context -- to Facebook, 'public' means everyone in the world, whether they're a Facebook member or not."

  • Your Vacation Countdown

    <a href="http://finance.yahoo.com/family-home/article/110674/6-things-you-should-never-reveal-on-facebook" target="_hplink">CBSMoneyWatch.com</a> warns social network users that counting down the days to a vacation can be as negligent as stating how many days the vacation will last. "There may be a better way to say 'Rob me, please' than posting something along the lines of: 'Count-down to Maui! Two days and Ritz Carlton, here we come!' on [a social networking site]. But it's hard to think of one. Post the photos on Facebook when you return, if you like. But don't invite criminals in by telling them specifically when you'll be gone," MoneyWatch <a href="http://finance.yahoo.com/family-home/article/110674/6-things-you-should-never-reveal-on-facebook" target="_hplink">writes</a>.

  • Your Child's Name

    Identity thieves also target children. "Don't use a child's name in photo tags or captions," <a href="http://www.consumerreports.org/cro/magazine-archive/2010/june/electronics-computers/social-insecurity/7-things-to-stop-doing-on-facebook/index.htm" target="_hplink">writes</a> Consumer Reports. "If someone else does, delete it by clicking on Remove Tag. If your child isn't on Facebook and someone includes his or her name in a caption, ask that person to remove the name."

  • Your 'Risky' Behavior

    CBSMoneyWatch.com <a href="http://moneywatch.bnet.com/saving-money/blog/devil-details/6-things-you-should-never-reveal-on-facebook/2360/?tag=content;col1" target="_hplink">writes</a>: <blockquote>You take your classic Camaro out for street racing, soar above the hills in a hang glider, or smoke like a chimney? Insurers are increasingly turning to the web to figure out whether their applicants and customers are putting their lives or property at risk, according to Insure.com.</blockquote> There have been additional <a href="http://www.huffingtonpost.com/2010/02/22/facebook-twitter-users-co_n_471548.html" target="_hplink">reports</a> that insurance companies may adjust users' premiums based what they post to Facebook. Given that criminals are turning to high-tech tools like Google Street View and Facebook to target victims, "I wouldn't be surprised if, as social media grow in popularity and more location-based applications come to fore, insurance providers consider these in their pricing of an individual's risk," <a href="http://www.huffingtonpost.com/2010/02/22/facebook-twitter-users-co_n_471548.html" target="_hplink">says</a> Darren Black, head of home insurance for Confused.com.

  • The Layout Of Your Home

    <a href="http://identitytheft911.com/company/press/release.ext?sp=11132" target="_hplink">Identity Theft 911</a> reminds Facebook users never to post photos that reveal the layout of an apartment or home and the valuables therein.

  • Your Profile On Public Search

    Do you want your Facebook profile--even bare-bones information like your gender, name, and profile picture--appearing in a Google search? If not, you should should block your profile from appearing in search engine results. Consumer Reports <a href="http://www.consumerreports.org/cro/magazine-archive/2010/june/electronics-computers/social-insecurity/7-things-to-stop-doing-on-facebook/index.htm" target="_blank">advises</a> that doing so will "help prevent strangers from accessing your page." To change this privacy setting, go to Privacy Settings under Account, then Sharing on Facebook.

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