The user wouldn't have to pay anything to create an account, just to vote. Sure, spammers can farm large amounts of reputation through botnets, but that's reall

The user wouldn't have to pay anything to create an account, just to vote. Sure, spammers can farm large amounts of reputation through botnets, but that's really expensive: you're putting a cost on it. The returns are already not so high for disseminating this kind of spam. Having no reputation wouldn't mean you can't do anything -- just that what you do is less trusted and has lower priority.