Years ago, I had been involved in a gaming project. We were trying to create a Final Fantasy VI style game for the PC, it went nowhere and we've all since moved on with our lives. However, during that time frame we did use our own wiki page. It was a bit of a pain in the ass to manage. But I must have logged somewhere around 20k words just in world building for the wiki. It had everything from the history of the world to a good four or five page history of each character. It was pretty neat, but time consuming.
It wasn't actually hosted ON wikipedia, but it was one of those CC/Open source programs LIKE the real wikipedia. But, it was hosted on our own internal server.
But, in Steve's defense, I have seen a couple of self pub'd authors on Wiki.
I found this guy when I was seeing if my pen name existed on teh interwebs (it does)
http://en.wikipedia.org/wiki/David_Alexander_(author)
http://en.wikipedia.org/wiki/Jeremy_Robinson
Wonder if I should change my name, don't want to be associated with that guy. :/