Robert Scoble had a very interesting blog post recently. He said, "But Twitter isn’t where the real money is. Where is that? Getting businesses onto the social graph."
Reminded me of something Jim Champy says in Outsmart!: How to Do What Your Competitors Can't:
"Build a community, but tend to business. A lot of supposedly smart venture money is flowing into community-based Internet businesses such as YouTube and Facebook, which derive their profits solely from advertising. Making money in this way might be a viable business model, but, in my opinion, few of these businesses will survive as profit-making ventures."
I highly recommend Champy's book.