[_jb]

I don't know when that was, but at some point the rails (sexy) community pushed for git. That sure helped.

Edit: no pun intended ;)

[lylejohnson]

I agree that the Rails halo effect probably had a lot to do with it. That's certainly where I first heard about it.

[cheald]

Rails moved to Git in 2008, so I don't think that's it.