I kind of think that a movement can be a form of a community. In that it is still a group of people with common interests, knowledge, language and established rules. The prime difference I think is that movements are more action oriented to complete specific goals.
My sister in law works for Blue Cross in NC and sent me this to invite me to join. I did not join, but I'm completely fasicnated to see how this type of social networking grouped around medicine and health will work out. Yes, WebMD and other SN's related to health exist, but this one is directly sponsored and supported by a health care company.
I find this interesting because it begins the notion of transforming an online content source to a book, and moreover it is built around a social application with the potential for multiple authors. Essentially, Anthologize allows the authors of the blog to take specific posts and generate them into a book. By the way, the developers of this are from the Center for History and New Media, see the next post!
I think I plug this every year in a class, but it is a conference for library developers. Essentially the coders and hackers who represent those most likely to bring theory to production regarding many of the ideas that come out of Social Informatics. I've gone to 2007 to now and its very interesting on many levels.