Ah, wikis.
In my experience, wikis tend to either go really well, and produce amazing results, or else they go very badly, and result in hurt feelings and flame wars. Or else, as is the case with the few I've set up with my on-line friends, they go well for a few weeks, and then everyone gets bored with them and moves on to something else.
To be honest, I'm not quite sure how a wiki would work within a library in general. A lot of the wikis linked to on the Learning 2.0 blog certainly look interesting...but they don't seem to get a lot of traffic. I love the idea behind the "Library Success: A Best Practices Wiki"...but again, I can't help but notice that it's nowhere near as active as, say, the plain old forums over at LIS news. The main problem I have with wikis is that they don't work unless everyone pitches in and plays nice - and how often does that happen on the internet? As has been demonstarted with Learning 2.0, it can be hard to get everyone to work together on the same thing unless you make them, and when you make them, you're going to end up with a few participants who are...less than enthusiatic about the whole thing. Which, with wikis in particular, leads to junk postings, people deleting other entries accidentally or out of spite, and plenty of infighting. Of course, you can always create resrictions on who can post, what can be posted, and who can edit or remove other participants' entries, and you can have a group of users go through the entries from time to time and remove entries and/or participants who don't follow the rules. But...if you're going to do that, why not just set up a forum and be done with it?