Just an example of long-term unreverted vandalism for your amusement:
http://en.wikipedia.org/w/index.php?title=Art_Tatum&diff=32294907&ol...
External links, language links, categories and a sound sample reference were deleted in December 2005 by an anon. The sound sample itself was permanently deleted a month later citing "orphaned fair use". The lost sections were progressively rebuilt by human effort over the 18 months following, except for the sound sample which remains lost.
-- Tim Starling