My 3 cents, and I apologize, its off the origional subject.
Bag hanging doesn't work in areas where the bears are already habituated, you can hang an empty bag, and bears that have associated hanging bags with food will still go after them, and the sharp ones have figured out how to get them. The same applies to canisters and sacks in areas where bears associate them with food. set an empty canister out in an area with bears that associate them with food, and bears will attempt entry. Of course the point in using such methods and products is to prevent that initial human/food association.
We built a tent for YNP based on the same principal as our Palisade bag, specificaly for a bear that was targeting tents. A biologist set the tent up in the area that the tent targeting bear was hanging out, and before she could even get the cameras set up on the area, the "tent bear" showed up. This bears "reward association" was tents. The bear made a beeline to the tent, while the biologist cautiously exited the area. Several months later this bear has not been know to again target tents.
Bears with food association "issues" can be drawn into areas where there is human activity, regardless of food "availabilty". Once a bear gets a food reward, that bear will continue to assosciate items that are related to previous food rewards with the "potential" of additional food rewards. This association may be anchored in past rewards with packs, tents, a canister with a lid that was left off, campsites, etc. Of course anything that smells of food will also be an attractant, I would not put too much stock in odor "proof" sacks, the latest research suggests that a bears sense of smell may be as much as 50 times better than a trailing hound. So if there is a bear in the area that has a broad food association, ie. simple human presense, then they can smell you as much as a mile away, and may be drawn in.