Honestly, I don't think we should be "registering" sex offenders. It's tantamount to punishment after the sentence has been served. It's hard enough for people who've served serious jail time to get jobs and find decent living since applications for all of those usually all have the question if the applicant has ever served time in jail.
So now we have a situation where someone has served time for being a "sex offender" which can range from urinating in public, to sleeping with someone a year or two younger than you (but who was underage and you lived in a state without a "Romeo and Juliet Law") but you still maintain a serious relationship with all the way up to child diddling/rape.
Registering as a sex-offender doesn't account for this wide range of circumstances and the net result is that vast majority of people who were in for more minor offense are hurt for it. This will more-than-likely lead to them either having to live in a high-crime area with lower standards or possibly turn to a life of crime themselves just to exist.
Now, I admit that if you live in a neighborhood you might want to know if the person down the block served time for raping a child. But I am not sure how to account for that without possibly violating a person's right to privacy and without continuing to punish them after they've paid their debt to society through jail-time.
But, at the very least, we need to account for the degrees of separation there is between "urinating in public" and "child rapist." Maybe only have the registry apply to the more serious offenses? But if we do that then I'd have to argue for some sort of registry for people who've served time for other violent crimes like "traditional" rape, murder, robbery, auto-theft and so on.
It's, frankly, a little un-fair to single out one "class" of criminals because we live in a society with the Maude Flanders-ian "think of the children!" mentality.