As I mentioned in my previous post, I have used a wiki before to write a group paper. I personally loved the experience. I especially liked the fact it saves previous drafts so you can always go back and see who made what changes and you don't lose the earlier drafts. Of course, it was also very convenient because my group was able to write a paper without having to meet face to face. This could be just as beneficial in a library setting for staff to colloborate or even libraries in different parts of the world.
I am familiar with wikipedia itself because I use it all the time! It is so convenient. If I need a quick summary of a topic I always go there and it makes a great jumping off point to learn more. I also took a look at some popular wikis and found a Harry Potter one- http://harrypotter.wikia.com/wiki/Main_Page