In my years of camping I've never lost anything, but then again I take precautions and don't leave expensive stuff out unsecured. So that's probably why I haven't lost anything. I'll leave chairs out and things like that, but the bikes get locked up and when I did have a Honda 2000 generator is most certainly got locked up.
And it's not necessarily your fellow campers you have to worry about. It's the meth heads who live within bike riding or walking distance. They'll steal anything and everything and I bet there is not too many places in the Country where you won't find meth heads close by. I have security cameras at my business and I review the weekend video every Monday morning. As soon as the sun sets on Friday night the tweakers come out like cock roaches. Mostly on bikes, mostly towing some type of trailer behind the bike. They dig through the dumpsters and trash cans and look for anything of value that may have been left out. I've even got video of them stealing all the copper out of air conditioner units at my neighbors shop too. If they identify a campground as a target rich environment, then they'll be there. I got with my neighbors at my business and we have almost dried the problem up just by putting up some more lights behind the buildings and by locking up all the dumpsters at night. When they couldn't get into the trash they eventually have almost completely quit coming by.