Back in the 1980s, Yosemite National Park was having a serious problem with bears: They would wander into campgrounds and break into the garbage bins. This put both bears and people at risk. So the Park Service started installing armored garbage cans that were tricky to open — you had to swing a latch, align two bits of handle, that sort of thing. But it turns out it's actually quite tricky to get the design of these cans just right. Make it too complex and people can't get them open to put away their garbage in the first place. Said one park ranger, "There is considerable overlap between the intelligence of the smartest bears and the dumbest tourists."
P.S. JBTW, my userpic shows a garbage can in a shape of a bear that I saw back in 1997 in Bern. There were lots of them and each one had some sort of a detector, so that when you threw something into the can, it made funny belching sounds and then said "thank you" in a random language (our testing showed the bears knew at least ten languages, including Russian).