faberNovel Consulting has released a research paper on social networks. The paper is an excellent theoretical overview of social networks and the trends in this important market. I particularly liked the following two slides, showing the types of social networks and how they're positioned. Interesting that in terms of identity, Facebook and MySpace are at opposite ends of the spectrum - Facebook is viewed as "real identity", whereas MySpace is "fanntasized identity"! The whole set of slides is below, via Slideshare.
Here is the full paper, in slideshow format:
The study also has some interesting analysis of business social networking, a subject we've been looking into recently.