I visited the various wiki sites mentioned. I skimmed a study done by John Walker where he studied the differences between wikis and blogs. His 99 page work (I skimmed parts) includes a study he undertook. He concluded that wikis depend on activity participation by individuals who support the aims of the wiki for them to be successful. Walker felt that they were not easy to use if one wanted to make a "meaningful contribution".
Where could they be used in a library setting? staff only on a private wiki- proceedure manuals could be developed using a wiki. Staff could work on this together
for the public - the subject guides at St. Joseph's County Public Library gave a good example of a use of a wiki. Reading clubs for adults where not everyone was reading the same book. At Princton Public Library - booklovers wiki - participants reviewed and rated books. The titles were linked to their catalog.
In Walker's study he included a chart with the comparisons. Wikis were shown to be best for documents with a longer life and that you would expect to edit and refine as more is learnt.