The rise of Twitter has been accompanied by a rash of fake stories that spread like wildfire on the social networking site before anyone had a chance to deny them. This week saw MSNBC, for one, taken in by erroneous reports on Twitter that another Icelandic volcano had erupted. Beyond the premature reports of celebrity deaths that routinely crop up, here's a list of Twitter hoaxes or scare stories that fooled thousands:

The Sarkozy affair(s)
The rumor: That both French President Nicolas Sarkozy and his wife, Carla Bruni, were involved in adulterous affairs. (March)
The fallout: The story was all over the British and Italian newspapers—though French privacy laws meant it received little coverage in Sarkozy's home nation.
The denial: French magazine L'Express reported that the rumor was started as a hoax by a French trainee journalist "to see how easy it was to get an unverified assertion" to spread from Twitter to blogs and the mainstream media. By the looks of things, writes John Lichfield in Britain's Independent, "he succeeded beyond his wildest dreams."

Airlines team up to fly doctors to Haiti for free
The rumor: That doctors who wanted to fly to Haiti to help earthquake sufferers would be taken for free by American Airlines and JetBlue. (January)
The fallout: American Airlines was flooded with calls from doctors across the U.S. hoping to fly out to help victims of the quake.
The denial: "Last night's hoax on Twitter about American and JetBlue flying doctors and nurses to Haiti for free was just that—a hoax. We don't know who is responsible, but it's a very low thing to do," an American Airlines spokesman told CNN.

Caltech's earthquake prediction

The rumor: That scientists at Caltech were predicting a major earthquake would hit California within a few days. (April)
The fallout: Caltech and local police and emergency services were "inundated by phone calls" after the rumors went viral.
The denial: "We cannot predict earthquakes," said a Caltech spokesman.

The overturning of Proposition 8
The rumor: That Proposition 8, California's law banning gay marriage, had been overturned. (May 2009)
The fallout: The news spread like wildfire, with thousands retweeting a link to Los Angeles Times and ABC News stories about the overturning of the ban.
The denial: Not so much a denial as a clarification: both the Times story and the ABC News story were over a year old and referred to an earlier ban being lifted.

The philosophical father of Twitter joins the site
The rumor: That legendary German philosopher Jürgen Habermas, whose ideas on the "public sphere" predicted the rise of social networking, had joined Twitter. (February)
The fallout: Unlike most fake Twitter accounts, which are shut down or called out as fakes almost immediately, Habermas' "account" was "verified" by Alan Rusbridger, the editor of Britain's Guardian, and quickly gained over 7,000 followers. The "philosophy blogosphere went into a frenzy" over the new celebrity tweeter.
The denial: Those brainy followers began to smell a hoax when the noted theorist began posting statements such as "Sprechen Sie Deutsch, bitte?" (Do you speak German, please?). Eventually, the real Habermas emerged to confirm it was a hoax.