Once word gets out among scumbags, you never know how many them have heard about or been in that house. Say if a couple went in the first time, an then one comes back later with someone else, who later comes back with someone else a different time. Unfortunately if that property is on the scumbag grapevine, catching one lot of them most probably won't be the end of it. So, yes, bear traps.
The next thing you know there will be PVC pipes sticking out of the ground.