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.