Keeping an eye on sex offenders can be a really bad idea if it takes your eye off your child. New York's University at Albany reported for a twenty year period more than 95% of arrests for sex crimes were first-time-offenders, not registered sex offenders. Indiana Department of Corrections reported for 2008 that "only" 1.5% of Indiana sex offenders returned for a sex crime within three years of their release. Ohio, in a ten-year study reported that two-thirds of sex offenders who recidiviated did so within three years. US Dept of Justice found that 93% of child sexual assaults were committed by either family (34%) or acquaintances (59%).
Adam Walsh's mother left him alone at a toy display while she went just around the corner, out of sight, for no more than five or ten minuets. They found his severed head a few weeks later.
Carlie Brucia was walking home alone after spending the night at a friend house. A business' parking lot surveilance camera caught a man grabbing her arm and leading her away. They found her body a few days later behind a church.
Sommer Thompson ran ahead of the group she was supposed to be walking home from school with. He body was found in a land-fill a couple of weeks later. There were more than 160 sex offenders living within 10 miles of her home.
Samantha Runnion was playing in her front-yard while her grandmother was inside. They found her body along a rural rode the next day.
What these and too many other tragedies have in common is that the men who commited these crime had never been convicted of any sex crime. You must have been convicted of a sex crime to be listed on a sex offender registry and these people weren't.
The point is that watching registered sex offenders places your focus on a very small fraction of the threat to your children. Watching your child covers all threats.
Jaycee Dugard, the woman recovered at age 29 after being abducted at age 11? Her step-father saw the grey sedan make a u-turn at Jaycee's school bus stop, a woman get out and pull her into the car and take off. He just wasn't close enough to get a license plate number or do anything else to stop it.