I'm not sure ... the thing that I like about my social networking spaces is that I connect to all my friends ... and I can see what they're up to ...
But for learning? I think perhaps informal learning rather ... because the thing I like about facebook is that I have one friend who tends to post things on the news and have discussion on the articles it's through him that I'm able to find out a lot that is happening in the world news.
True, however maybe there is more of a market for these things in the distance learning sphere. I believe that OU students use Facebook to connect to other students on the same course, and there has been some experimentation with Facebook apps. Like you say, a kind of transition between informal/semi-formal learning and social.......social learning?