This could be a smart move...
Microsoft had a very nice "social network" which even integrated seemingly within their Windows Phone environment as well as their XBox environment. Heck; it even blended in perfectly with their "web tools". I'm talking of course about their Messenger / MSN service. It could be used on PC, it could be used on WP and even using nothing more than a browser would give you access. It was a very nice alternative.
Of course, directly in line with their "Lets tick off our customer base" (as I like to call it) Microsoft discontinued messenger and the whole social media environment behind it; all instant messaging needs to be handled by Skype. Well; I'll pass. I don't like "free" services which constantly spam you with "buy more credits" advertisement. Even on neutral ground such as your profile page. Really; WTF?
So yeah; if they manage to pull this off and also introduce a desktop counterpart which can run on your PC (like Messenger could) then I think they may very well be filling in a huge gap on WP.
And who knows; it could also just as well get them some interest for their phone line as well...