A social network with file sharing. Why not?

Idea: A social utility that creates massive data clouds around a user's files and his friends files.

I'm building a better social utility and need opinions on why file serving in a social network may be good or not so good idea.

Background: Photos, videos and even messages are simply files accessible by one's social network.

Example: User A shares his favorite songs in an upload. His/Her friends may then listen to those tracks online.

Why don't we have a social utility that allows ANY file sharing/exchanging?