Not directly related, but this made me think of how different a "social network" built on version control is from a typical social network.

Github users are interested more in code than in people. Sure, you can use it to follow your favorite coders and technology people that you respect and look up to, but I have a feeling most people aren't doing that too much.

Like most developers, I use Github extensively to obtain open-source code that I use in projects. Sometimes, I explore Github to look for new things, or see what kind of projects are popular since I've last checked (maybe once or twice a year). Usually, it is the canonical source of information for large open-source projects; the code lives there and issues / bug reports live there. While using it in this manner, I don't look so much at who is posting comments / commits, as I do at the content of the commit or comments on issues, and whether the information is relevant to me.

depends on how the social network is monetized. There are no ads on Github. Unless github is selling user data to third parties, their monetization method is well known (paid enterprise features)