I have a set of these hitch pin and trailer coupler locks.
http://www.campingworld.com/shopping...ler-locks/1621
Some clown might pull the little clip out of the hitch pin and then it could work its way out miles down the road. the drawbar would come out of the receiver and I'd have a BIG problem.
Also, a lock in the coupler prevents some clown from popping the latch up while you are eating or whatever. These locks make that nearly impossible.
Tom