Github's likely emergence as Silicon Valley's latest unicorn could lead to conflict between its open source ideals and the pressures of a multibillion-dollar exit.
Very true.
GitHub just is a nice convenient example used by a community (the FLOSS one) that should know better, with a past example that has already gone wrong (SourceForge).
Not that GitLab is a big improvement: the hosted version is based on the proprietary edition, so there is no guarantee that a migration to a self-hosted community edition will be seamless.
Also, that is exactly what we used to say with gitolite, and it didn't go that well. :(
Personally I'm hosting my personal projects on a gitolite+gitweb at home, and I'm looking forward to see git integration in friendica for the stuff I want to publish (Friendica and not pump.io because in friendica there is already something done, see e.g. http://social.gl-como.it/projects/gl-como/sito/commits/master but of course both would be fine)