I think we might be able to create communities of readers with Wikis this way; I have a book journal in which I record the books I've read, and I record in a book wiki that I've really enjoyed "No Pretty Pictures; a Child of War," by Anita Lobel. Someone else could then comment that they thought Lobel's book is a good companion to Anne Frank's Diary, being that Lobel survived the camps. In this way we could harness the collective knowledge of our librarians and use it to provide our customers with better service.
You know how bookstores frequently have a collection called "Employee picks?" Why couldn't we do something like that using a Wiki? The Princeton Library did, and I think it looks like a good idea.