Truckin, well, that's an issue with most any wiki, but it seems to usually work out OK. At the worst, it shouldn't be any worse than the conflicting information that sometimes show up in regular forum threads anyway. It will require some respect on the part of the users, and there may be some methods of moderation in place (not that familiar with the features of the usual wiki packages)
I think a wiki is a great idea because many of the FAQ threads are very long and detailed, and I think we can all appreciate the effort of those who wrote them; but those pose a few problems... if you have one smaller bit of information that would be better as part of a larger FAQ, you would either have to take the time to write a full FAQ, or get someone else to edit into their existing one... not really that suited to being a collaboration between many people with different expertise. And any edits (additions or corrections) to an existing FAQ require the original poster (or maybe a mod) to be on the ball and do the modification. I see a lot of really thoughtful and intelligent posts in regular threads on this forum, and it would be nice to see more of that actually collected in one place.
I bet we would see more contributions to building a good, solid FAQ/Guide that encompasses everything if a wiki was made. And, due to the organization of a wiki (such as being able to click key terms and be taken to articles with info about them), it should be easier to navigate, and ANYTHING we can do to make the FAQ easy enough that more noobs read it before asking obvious questions, is a good thing :P