First I want to know how to post to the sandbox! I joined the wiki, signed in, what else? geez!
Wiki's seem to me to be less fancy blogs that can be less public. Wiki's seem easier to restrict who sees it. It is fascinating to see who reads our blogs and I suspect the person in Australia found mine because there is a university there that is also doing 23 things. Read about that in wired - very cool to be part of it.
Wikipedia was obviously the start of the wiki, and the most famous one. Wiki's can be updated by anyone if they are public, which is an advantage and a disadvantage. Everyone may think they are an expert but they are not. I want my information from sources that are expert.
We use wiki's, as do other library programs. Here is the Denton 23 things wiki I found this using a wiki search tool.
When we use a wikis to teach we can restrict who sees it and who updates it (which is probably why I can't post to the sandbox yet!). For education purposes it is a very powerful tool for communication.