Check out steemit. It's a social media and it runs on the Ethereum network using steem tokens.
I agree that a decentralized social network would be beneficial.
Steemit is a great social media platform, It's more of a blogging platform. There's also a project called Akasha, also powered by Ethereum and Vitalik as actually an advisor for it, the beta is currently running (and it is a bit slow). I really like the idea of it - you should check it out.