they almost always bother to have a go at $saturated_market, since they have enough of a thought-gravity-well to get /some/ people using it
FTA:
Note that Socl is a research project, so it's possible that it won't ever get released as a mainstream product
Like Google, Microsoft has a huge user base in their Live product family. Adding social features to that seems like ano-brainer to me. The recommended strategy for this space is "if you can't dominate, fragment".