I came across this interesting project that aims to stop online pedophiles by setting 100,000 online honeytraps. It calls for 100,000 volunteer adults to post online profiles in various services posing as minors. They then use these a bait and wait to be contacted by pedophiles. Once contacted they basically set the hook and then do a sting operation with the help of law enforcement agents. The idea is that by doing this the odds of an online profile of a minor actually being a trap, and thus the odds of a pedophile getting caught are increased enough to scare and/or catch the majority of online sexual predators. It's kind of like a "neighborhood watch" for the Web. I don't know how legal it is, but at least it makes sense statistically.
Of course, there's an easier way to catch pedophiles these days: Just visit the US House of Representatives.