[hamburglar]

No, I think you get it. It's the equivalent of doing a password reset every time, generating a new random password each time, and simply never writing that password down. The idea is interesting but it has a few drawbacks. The one drawback that hasn't been pointed out by any comments I've seen is that email suuuuuucks as a transport for something you want to happen quickly (e.g. logging in). Occasional hiccups in delivery and spam false positives make it a serious pain in the butt if you have to receive an email in order to log in somewhere.