As Facebook executives embark on a road show to pitch the stock to investors for an expected Initial Public Offer later this month, it makes me think of cigarettes, booze, gambling, even guns.

Those types of companies produce toxic consumables that have made many an investor filthy rich by betting people will lap up things that are ultimately harming them, or others. Investment advisers call holding these companies' stock to be part of a "sin portfolio."

These companies have no trouble finding "realistic" investors who look at the big trends in society, and see betting on firms that take advantage of these trends as the best path for financial returns. We may not like it, but it's a fact of life in the market.

I spend a lot of time on Facebook, and on other social media networks as well. I am most definitely not "anti-Facebook," but I do have concerns.

Facebook -- with its ubiquitous threat to privacy -- is quickly making the case that it deserves to be a part of the sin portfolio investment strategy.

To makes this case, we need to show that, like tobacco and alcohol, Facebook's profits are tied to a morally questionable business model; one that is addictive, and insidious for users. For all the good that Zuckerberg's company has done for reconnecting people, and letting them communicate with one another, Facebook exists to extract from those relationships the secrets of what makes us tick consumers. They sell these opportune marketing moments to the highest bidder. In other words, Facebook leverages -- and abuses -- our privacy for its own profits.

Many of us have had friends who got caught up in multi-level marketing companies like Amway or Mary Kay cosmetics. It's annoying, and disheartening when someone close to you transforms your friendship into a sales channel. It often leads to alienation, even excommunication. What Facebook is trying to do is use each and every user's identity, relationships, friendships, and status, as a sales channel. If it's not acceptable when a friend does this, how is it acceptable for Facebook? At the very least this distracts from our relationships, at the worst it degrades them.

There's also something insidious about Facebook versus big tobacco: Smokers actively choose to smoke, and make continued decisions to be the customers of tobacco companies. Facebook users aren't even the company's customers, they're inventory.

Advertisers are the most important stakeholder at Facebook, not the close to one billion users. Sure, users are essential, but Facebook routinely pushes the boundaries when it comes to privacy so that it can serve the needs of advertisers first and foremost. Facebook has repeatedly faced controversy over its privacy policies.

Invariably, the public mea culpa comes from Facebook when users realize their privacy has been infringed without their knowledge. It reminds me of a golfing buddy who rarely tells his wife when he plays "because it's easier to beg for forgiveness than it is to get permission."

Over and over, Facebook has proven itself counter to the philosophy developed by Ontario Privacy Commissioner Ann Cavoukian called "Privacy By Design." It is the notion of embedding privacy into the design of technology and it is an approach that is now enjoying widespread currency well beyond Canada's borders, but not at Facebook.

There's an all-too-common response when the issue of privacy is raised with Facebook: if you find Facebook so distasteful, don't use it. The problem is that this isn't really a fair position to take. Social networks are prone to monopolistic positions because of network effects. Even Google has failed to seriously compete with Facebook. Facebook's become a part of life for socializing. In fact, there's a long-standing saying (in the context of the web): even if you're not on Facebook, you're on Facebook.

Is FB going to be a good buy when it is scheduled to go public May 18? For the investor, maybe. But for society, not so much if the company continues to flout users' privacy to serve advertisers better. Buy it if you like, but know what it is: digital cigarettes.

Follow Paul Barter on Twitter: www.twitter.com/barterpaul