They named windows before most people knew what a windowing UI was. They're trying to come into an already mature market, they won't be able to create much awareness with a generic brand.
Think how it will be referred to on broadcast news which loves quoting what people are saying on social networking sites as it's cheap to produce (and is how most people will first hear of it).
"we've been getting lots of reports in via Twitter, Google Plus, Facebook and Social"
"there have been outpourings of grief on the social networking sites Facebook, Twitter, Google Plus and Social"
They might call it "Microsoft Social" but that's a bit long.
I don't think Google Plus is much better in that regard. Facebook and Twitter are the better brands at two syllables and not having any association outside of social networking.