This is closer to how we work at internally at GitHub. Everyone files pull requests for non trivial changes, and are responsible for merging and deploying them safely. Edit: This works because we all have push access of course.

This changes when you consider open source projects. Any change that is simple enough that I can scan and give my thumbs up, is likely one I can scan and click the merge button. Immediate Travis-CI results tell me everything is happy.

Anything where the merge button isn't sufficient is probably not something I'd like a stranger to push to my repository. If they're not a stranger, I'd seriously think about sharing collaboration access.

But hey, we're not necessarily done with Pull Requests. I have various ideas like this I'd like to explore at some point.