This is an interesting step in the utilization of Wikis. Wiki Books is a site that allows people to “build” books collectively (ideally). It is also available in a number of languages (I’m sure that translations are not far off, if they don’t already exist).
I have to admit that I haven’t found any “books” that have been significantly developed yet. However, if Wikipedia is any indication, they are not far off.
APA is going to have to figure out a better way to cite these kind of sources. Maybe instead of author, they could indicate “consensus”?