Felipe, this is really cool. I've posted a comment here: http://tracker.moodle.org/browse/CONTRIB-1444
Personally, I'd like the confirmation need to be optional, and able ot be switched on and off. ie in some cases, all I want to know is that people have self registered in two ways: e-mail, and in some sort of dashboard.
And, wll done for not doing this as a hack.