A fascinating example of how erroneous information on Wikipedia leaks out into the web, turns into citable information that can then be recycled as verifiable back to Wikipedia. A Wikipedia editor in February spotted the following strange edit made in November 2002 – nearly 10 years ago - mentioning a scientist’s claim that the Van Allen belt is the result of volcanic activity. Which is of course nonsense. The editor Googled for this and got plenty of hits, and it nearly went unchallenged. However, suspecting that the age of the Wikipedia entry had caused this claim to become accepted fact, he emailed the scientist, who confirmed it was nonsense, and the edit was finally reverted on 18 February 2011.
The ensuing discussion is on the Wikipedia Astronomy project page.