[bzbarsky]

There are absolutely lock-in effects.

You want to participate in web standards groups? You have to use github to do so in any sort of effective fashion.

Same thing for various open-source projects.

The _owner_ of a project has a bit more say in things, though I've heard some people claim that in order to attract contributors a project must be on GitHub nowadays, because many people will fail (or refuse) to participate in any way other than GitHub pull requests.

So I agree with you about Apple and YouTube; I just think GitHub is closer to them than you think it is...