Microsoft has publicly launched their own social network So.cl for everyone.
So.cl has been online for a while now but needed an invite to join.
The company is now aiming to take on Facebook with this new network. They allow the users to connect with their existing social accounts. There is deep integration with Microsoft services like Bing.
The idea has been to enable collaborative features powered by online services so that students can work on projects together.
It is not clear what the long term goal is considering Microsoft is already a pretty big partner of Facebook.