I think it's a great idea, but not without flaws. The biggest problem is catching and prosecuting these scumbags, and then of course, enforcing their registration. The system has a hard enough time keeping track of the sex offenders, and I'm certain that the majority of John Q. Public (not PTers), would not particularly want to see their tax money spent for this. But yeah - something definitely needs to be done, and this is an idea in the right direction.