Is Github the most important social network?

John G. Norman:

TL;DR: GitHub is the largest public repository of the everyday experience of work. Ever. If you’re a scholar or journalist interested in collaboration, this is perhaps the most important archive you will find regarding what actually happens as people work together.

I do think Github is great and on the long run it is a rich log of the history and evolution of software development. That is one of the fields that is pushing the human race forward. But on a mass scale, it can not be as relevant as Twitter, Facebook or Linkein.