You hit on a good point--visibility and accessibility. The only place I had someone try to steal something was in DuBois, WY. The tenting area of the campground (a private one) was next to a road that led to a trailer park or some sort of residential area, with nothing but a post rail fence for "security." I stupidly left my stove out. Two kids drove by and stopped. One jumped out and headed for the fence. I was sitting outside the laundry room and started running towards my tent. The kid jumped back in car and they took off.

Normally, I don't worry much at all. I have taken ay least one week+ tour without a lock. But when I am camping in a place--either public or private--where the population has easy visibility and access--I take extra precautions like to leaving anything of value visible, even if that means simply tossing it in my tent.