i let anybody touch my shit, i really don't care. but if they break it they buy me a new one/pay me the original cost, depends how mad i am. and if they don't agree, then they can stay the fuck away from my cameras.
i once had a gaper snowboarder pick up my camera bag thinking it was his backpack (i was way downhill), and then he just said 'wait this isn't mine' and i had to watch helplessly as he dropped my bag from like 4 feet up. when i retrieved it, the viewfinder had snapped off my camera (way back when i had a VX), and the gaper was long gone.