I love wikis. They are such an amazing tool and it was really interesting to find out how they are being used. I couldn't believe that they have been around since the nineties (almost as old as I am :)), but it's great to see how they are being embraced now.
My favorite wiki is of course Wikipedia it is such an amazing body of information and it is my first port of call when I'm looking something up. People go on about how unreliable it is but, I've never had a problem and the many people that add to it daily are amazing.
The possibilities for their use in libraries are very fascinating. One of the best ideas I read about was to try and make the library page for a specific title on the catalog like the ones on Amazon. I am on Amazon almost every day looking at books, adding to my ever growing wish list and reading other people's review's about books I am interested in. Having this kind of system in a library catalog would be great as having one local to New Zealand would be a great step.
I think it is important to have some moderation by trained librarians like the SJCPL subject guides, but still encourage ordinary user imput as that is the way to build useful and reliable websites.