Most social activity generates no revenue. It's tragic that we are moving towards a society which sees every relationship as mediated by economic utility.
It shouldn't be a business. It should be a sustainable project. The moment you make it a business, it looses its core value - "by users, for users". That said, the project needs to sustain development and growth of course. The difference is in the goal. Business' goal is to make money, and it's driven by for profit reasons. Such kind of project's goal should be to make a good (user oriented, privacy protecting and so on) social network, and it should be driven by that reason.
And yet almost all businesses/organizations that facilitate human social activity extract some sort of profit: the postal service, telephone companies, ISPs, bars/pubs, and churches (for the cynic), to name a few.
