We were at DTD in Anaheim. My DD and I were in a shop. When we came out, my DH and DS are talking to security CMs, and some more are talking to a man sitting on a bench, looking through his wallet. It turns out the guy was a perv, and my husband and son caught him photographing the backside of a little girl about 7 or 8 who had bent over to tie her shoe. The CMs checked the creep's ID, then told him to leave and that they would be watching for him. They told my DH that they wouldn't call the police, because technically, the creep hadn't committed a crime.
Something similar happened with our DD in Vegas. Keep an eye out around your kids (and everyone else's, too).