I have noticed that there are at least two sex offenders in my town living on streets where there are elementary schools.
First, "sex offender" is not the same thing as "predatory sex offender" is not the same thing as "child sex offender." Second, as others point out on FR, some "sex offenders" are folks caught urinating in public, or teens with younger girlfriends. Third, of "child sex offenders" the vast majority were known to their victims, and the vast majority of those were family members.
The "leap out of the bushes" child sex offender is in fact a quite rare thing.
Oh yes, I almost forgot. According to federal studies (search for "U.S. Department of Justice Statistics"), over half the sex offense convictions every year are First-Time convictions. And when it comes to child sex offenders, the number goes up way higher.
Also, zoning laws around the country have been extremely counterproductive. In Iowa OVER HALF the registered sex offenders disappeared when they enacted their zoning law. Think about it a minute: they're homeless, they're probably unemployed, they have Nothing To Lose anymore -- and you have no idea where they are. Just like the fellow in this article.
The politicians are actually making it more dangerous for you and yours, not less. But the public remains ignorant of the real issues so they get away with with selling feel-good sounds-good snake-oil nostrums.