[brand]

Open source does not thrive on the fuel of non-profit alone. Red Hat and Sun are for-profit, but they're major contributors to open-source projects.

Open source is successful with not-for-profit models because people like hacking on open source. I don't think that's necessarily impossible for a social network, because people like to waste a lot of their lives on social networks, but are open-source hackers going to be interested in working on a project they aren't interested in using? I'm assuming that the primary appeal of social networks has long moved past the techie demographic.