I pay for Github because the few private repositories I have benefit from Github's frequently expanding feature set and make it worth the cash I pay each month easily. I think it's worth it to support a service with an iteration cycle that actively benefits its users to the point where paying for it is worth it.

I feel the same about App.Net. They're constantly coming out with new things, such as the hugely-more-powerful-than-Twitter Messages API and the Files API, and they're enabling devs to build apps for ADN that are significantly better than the offerings for Twitter. All in all, I enjoy using ADN far more than I do Twitter, to the extent that it's worth paying for.

Bitbucket's free private repositories is a godsend to academic and other small-time projects. Github can keep their hold on "public code repos as social networking".

You do realize Github offers educational discounts and accounts? See: https://github.com/edu

GitHub offers free private repos for academia.

Github offers five, whilst Bitbucket offers what is in essence an unlimited account to academic users.

If you got the same value proposition out of App.net that you get from GitHub (plus the whole networking effects) that would be true.

But you get what out of App.net? Basically nothing.