Approximately around 10:45 PM Pacific Standard Time, Wikipedia (http://en.wikipedia.org/wiki/Main_Page) website was being hacked by GNAA (http://www.gnaa.us/)
Another Fellow WordPress Blogger actually got a screenshot of the hacked Wikipedia main page.
http://vondiggity.wordpress.com/2006/12/14/wikipedia-being-hacked-by-the-gnaa/
Wikipedia was actually fixing the page while it was being hacked.
In the meantime, GNAA posts a press release that somewhat explain the reason behind Wikipedia hack.
http://www.gnaa.us/pr.phtml?troll=gnaa-wikidel
The hack was a retalication against Wikipedia for GNAA article deletion.
At first glance, it seemed that it was merely a change made on the frontpage. But such changes could not be found in the page history. It is unknown if Wikipedia administrators/moderators could selectively delete the page history.