It just seems so backwards that making a concrete mailbox can get you sued by a jerk that intentionally drove into it. I can understand banning pitfalls and other actual traps, but why passive defensive deterrents? After all, it’s not like a bystander accidentally wandering onto your property is going to be injured by a random bolder you placed between your garden and the street.
(Edit): It seems I had a fundamental misunderstanding of US law. Thanks for indulging my curiosity!
My understanding is that booby traps, like landmines, harm indiscriminately. i.e. they harm whoever trips them and not a particular target. And they persist until triggered. So in effect you have a time and target independent death lottery.