that's pretty nonsense, since just about anywhere that is busy it's silly to just leave some multi-thousand dollar device out amongst strangers. As many have said, I'll leave a drink or some food out, but even beyond trusting people, I think it's rude to ask anyone to watch over anything but your seat or a beer / sandwich. I don't want to be responsible for your shit.
It is not as exciting as being an anarchist, or marching in an occupy protest, but helping out a fellow human being by watching their stuff with a smile probably makes more of a positive impact in the world.
