I'm not obsessed with Wikipedia -- it may only seem that way. The same could be said the New York Times, which ran two articles recently about Wikipedia.
The New York Times had an interesting article, "Seeing Corporate Fingerprints in Wikipedia Edits," makes the point that Wikipedia does not like corporate meddling on sites, and that it is now easier to find out who has edited those entries thanks to "wikiscanner.virgil.gr, created by a computer science graduate student, cross-references an edited entry on Wikipedia with the owner of the computer network where the change originated, using the Internet protocol address of the editor’s network."
Interestingly, the article found "most of the corporate revisions did not stay posted for long. Many Wikipedia entries are in a constant state of flux as they are edited and re-edited, and the site’s many regular volunteers and administrators tend to keep an eye out for bias."
The second article, "Defending Wikipedia's Impolite Side," provides an interesting look Wikipedia's perspective on "being punk'd" online. The bottom line: Wikipedia isn't doing much to correct possible defamation in entries.