In concept, I like the idea that most users can propose a site. The problem is that I also like the "one proposal per user per day rule".
It would appear that the low threshold for site proposals is driving a number of proposals being made in the same day by different 'users' with improbably similar profiles:
http://area51.stackexchange.com/proposals/3857/fostering-a-troll-free-stack-overflow http://area51.stackexchange.com/proposals/3826/the-hunting-of-vampires http://area51.stackexchange.com/proposals/3661/unanswerable-questions
Setting a higher bar for proposals than for voting might help protect against proposal noise.