I would argue that 10 million+ people have gotten jobs through LinkedIn [1]. And getting a job equates to at least $40,000 a year in income, and a direct improvement to people's lives. The existence of LinkedIn has been a part of ~$400 billion a year to the world's economy. I think Github is a tiny tiny tiny fraction of that in terms of its real-world effect on peoples lives.

[1] LinkedIn has 161 million user accounts, and assuming 5% of them have gotten jobs through the services which could be low. Around 4 billion candidate searches a month are done there. http://press.linkedin.com/about