"In a couple hundred nights in the Sierra I've never had a bear come into my camp."
Geez, back in the old days before bear canisters, we had to hang all of our food in Yosemite. The bears knew all of the common campsites, and they knew which trees could be attacked and which not. We've seen bears on the trail, bears in camp, and bears up in the trees. Then after bear canisters came around, the bears did not venture so much into camps. They seemed to learn that canisters were a waste of time for them. So, canisters seem to be much more foolproof than hanging, plastic bags, or the other methods.