I love wikis. Nothing screams collaboration, community, engagement and open access like wikis. And, by and large, i think wikipedia gets a bad rap; in my (extensive) experience trawling it, I find that the vast majority of contributors know what they're talking about and contribute because they care about the topics they're elucidating. On top of that, wikipedia's network of moderators does a great job flagging what's innacurate, biased, out-of-date, irrelevant, etc. It's an amazing development of social industry.
That said, I'm disappointed by some of what I found on libsuccess.org. I was excited to look through it, thinking, "Great! This is perfect for me as a young librarian. A one-stop shop of everything that works! Tried and true methods." Instead of an easily-digestible encyclopedia of practices, though, I found more of a directory of other websites, other sources and blogs and listings. I think that sort of misses the point of a wiki, where we would expect to find knowledge concentrated, not merely pointing to its dilute locations around the web. Not happy!
I did really love the notion of the wiki as repository of a library's community outreach events, as was the case with http://booklovers.pbworks.com. If I had been them, I would have kept that up beyond 2006. As a hopeless nostalgia-hound, I love the opportunity to look back at what I was reading years ago; a record of a summer book club is like a community-wide archive of literary memory, with full accounts of relevant criticism, discussions held, and reviews written. I'm definitely putting that on my best practices list.