This is mind-boggling. Think of the possibilities. Bringing down companies with a bit of crowdsourcing? Check.
The Wall Street Journal reports that Google News crawled an obscure reprint of an article from 2002 when United Airlines was on the brink of bankruptcy. United Airlines has since recovered but due to a missing dateline, Google News ran the story as today's news. The story was then picked up by other news aggregators and eventually headlined as a news flash on Bloomberg. This triggered automated trading programs to dump UAL, cratering the stock from $12 to $3 and evaporating 1.14 billion dollars (nearly United's total market cap today) in shareholder wealth. The stock recovered within the day to $10 and is now trading at $9.62, a market cap of $300M less than before Google ran the story.
The article makes clear that Google's news bot only noticed the old story because it has been voted up in popularity on the site of the South Florida Sun-Sentinel newspaper. The original thought was that stock manipulation may have been behind the incident, but this suspicion seems to be fading.
Source: Slashdot, "Automated News Crawling Evaporates $1.14B