The original author purposefully put up an error-ridden rough draft of an article about Wikipedia on Wikipedia, then told the editors to have at it. The result, with comments on the process. Several versions of the article were frozen to provide snapshots of its evolution. The first edited version catches all the spelling mistakes and most of the factual errors; later drafts get tighter and contain less Wikipedia jargon.
I haven't done much with wikis. I find the concept utterly fascinating but I've never been inclined to spend the time it would take to get involved, in both the editing and the community. I do use Wikipedia, though, and will refer students to it in their research, although always with the caveat that there's no peer review.