Alicia L. Cervini has published on her website a thesis called "Network Connections: An Analysis of Social Software that Turns Online Introductions into Offline Interactions " which takes a look at the modern social software platforms. There is an extensive analysis in the capabilities of these platforms with a touch of social networking theory, but the conclusions are too little founded on the theory of social networking to make a lasting impression. Though it'll be outdated soon, if you are interested now in these platforms and their role in the SN world, check it out at:

http://stage.itp.tsoa.nyu.edu/~alc287/thesis/