"...and once dated the girl's mother..."
THIS is the sentence I always look for in these cases. I blame the MOTHERS in many of these cases, as they're the ones putting their love lives before the safety of their children. These creeps LOOK for disfunctional or splintered families. You rarely see this happen when there's a stable FATHER in the picture.
And yes, I'm remembering the recent murder of Jessica, but I'll bet statistically, it's the boyfriends of the single/divorced mothers that are more often than not the perps. When parents are on the ball, it's more difficult for the perps to get through the first line of defense to the kids.
Even in Jessica's case, had it been a stable, two-parent household, her father would not have been spending the night at his girlfriend's the night Jessica was kidnapped. Until people realize the vital importance of stable, traditional mom and dad families, things will continue to get worse. Parents have a responsibility to their children to provide a normal, loving home instead of putting their own selfish desires first. I am not blaming parents but just stating facts. We are a very screwed-up society and I don't see things improving any time soon.