How legal is To Catch a Predator?

My husband and I saw this show last night, and we had a few questions that were really bothering us. Could this show be seen as entrapment? There were never any underage people actually involved, so does that have an effect on the legality? I know these are often some pretty sick men, but something just feels wrong about the way this is handled. Plus, can Dateline legally show their identities without consent?