But the latest conspiracy movement seems custom-made to underscore the need for a national debate on mental illness. Some of the Sandy Hook Truthers, as they've been dubbed, believe last month's mass shooting in Newtown, Conn., was a hoax.
The Obama administration perpetrated the hoax, the conspiracy theorists claim, in order to ratchet up support for tougher gun control measures.
They call themselves Operation Terror, and many of the movement's adherents appear to have ties to the so-called 9-11 truthers who have long held that the terrorist attacks of Sept. 11, 2001, were an inside job by the George W. Bush administration.
Their theories on the Dec. 14 shooting in Sandy Hook appear to lack any basis in fact, reality or common sense. But Google Trends suggests the movement is gaining momentum with both a Florida college professor and a libertarian Fox News anchor in Cincinnati questioning the official narrative on the events.
On various websites and blogs, some Sandy Hook truthers crow about the "smoking gun" they say proves the shooting was a hoax — a photo of President Barack Obama, backstage at a Newtown vigil two days after the shooting, a young blonde girl sitting on his lap.
They insist the girl is six-year-old Emilie Parker, one of the 20 child victims of the shooting. The Sandy Hook truthers claim her parents slipped up in their participation in the hoax, and allowed their eldest daughter to cuddle up to Obama.
"The story that she was killed at Sandy Hook is not possible, because here she is sitting on the president's lap after the shooting," intones the narrator of a YouTube video, one of dozens of its kind, this one the recipient of more than 260,000 web hits.
In fact, it's the dead girl's little sister.
The child's father, Robbie Parker, was also faking his profound despair when he tearfully addressed the media shortly after his daughter's murder, the believers claim, and was reading from cue cards.
The family members of the massacre's tiniest victims aren't the only ones being accused of such unthinkable fraud as they continue to grieve.
A town resident who sheltered six youngsters after they fled Sandy Hook Elementary School in terror is even facing harassment from some of the conspiracy theorists.
Gene Rosen, a 69-year-old pet-sitter, told Salon.com this week that he's getting phone calls and emails accusing him of fabricating his story.
One email read: "How are all those little students doing? You know, the ones that showed up at your house after the 'shooting.' What is the going rate for getting involved in a government-sponsored hoax anyway?"
Police are investigating the harassment. Rosen, who also comforted a frantic mother who came to his door looking for her deceased child, told Salon he's furious at anyone who believes in such an outrageous conspiracy theory.
"There must be some way to morally shame these people, because there were 20 dead children lying an eighth of a mile from my window all night long," he said.
"I am rageful about it, both for the children and for the mother of the child who came to my house looking for her son."
Other Newtown conspiracy theorists allege there were four perpetrators from Israeli special forces, and that it wasn't children who died, but a secret United Nations delegation.
Fox News's Ben Swann is among those doubting Adam Lanza was the only shooter.
A Florida college professor also suggested on his personal blog that the Sandy Hook shooting may not have played out the way many believe it did — if it happened at all.
"I said that there may very well be elements of that event that are synthetic to some degree, that are somewhat contrived," James Tracy, of Florida Atlantic University, recently told a local TV station in Boca Raton.
"I think that, overall, the media really did drop the ball. I don't think that the media have gotten to the bottom of some of the things that may have taken place there."
Conspiracy theories, indeed, are part of the national fabric of the United States.
A veritable cottage industry still surrounds the assassination of John F. Kennedy almost 50 years ago, with alleged culprits ranging from the CIA to the mob, Fidel Castro and Lyndon Johnson, or a combination of them all. One book even alleged a UFO connection.
During the Cold War, some believed Republican president Dwight D. Eisenhower was a Communist plant.
The 9-11 truthers assert that the twin towers of the World Trade Center in lower Manhattan were brought down by timed explosions by those working for the Bush administration. And it was a guided missile that hit the Pentagon, not a jetliner, they allege.
More recently, the so-called birther movement advanced the theory that Obama was born in Kenya, not in Hawaii, and is therefore an illegitimate president.
One expert on the American conspiracy theory phenomenon points out, however, that throughout the course of U.S. history, there have been no shortage of massive government coverups — and they've only served to encourage skeptics.
"There have been so many well-documented conspiracies in American history," James Broderick, a professor at New Jersey City University, said in an interview.
Broderick points to everything from weapons of mass destruction to Lance Armstrong's admission of longtime drug use after years of denials and Robert F. Kennedy's recent acknowledgement that his family has long believed the official government report on JFK's assassination was a whitewash.
"It does seem appalling the way conspiracy theorists, and many people in general, try to exploit for their own petty political purposes a national tragedy — it's sickening and disgraceful," said Broderick, the co-author of the 2008 book "Web of Conspiracy."
"But what the 9-11 truthers told me is what's truly sickening and disgraceful is to not look deeper, to just accept pat answers without asking questions."
Some of the people advancing theories of more than one shooter in Newtown might have their hearts in the right place, Broderick said.
"But of course there's also a segment who are just angry at the government and at Obama all the time — the people who believe he's a Muslim and a fascist and everything else — and they have jumped on the bandwagon, posted terrible things on the web and tried to fuel the fires in the most shameful ways."Suggest a correction