I've seen my share a wiki skeptics, as detailed in this post. Clay Shirky hits the nail on the head when he points out why they are resilient - it takes more effort to despoil a wiki than it takes to restore the original content. I saw this first hand a few years ago when a complete idiot decided that it was his god given right to deface pages here. He carried on for about a week and a half, gettting increasingly angry after each rollback of his graffiti - but he eventually gave up - because his bad behavior was more work than my restorations.
There are a few other really good points in the post that go beyond wikis - the introductory points about process, for instance. Ted Leung points out this followup. Ben Hyde clearly doesn't agree with Clay's process arguments - both points of view are worth reading.