Mr. Cohen's points seem sound and reasonable, with a couple of exception. Unfortunately they are not minor.
First, from all that I have read, it is apparent that a large part of the success of the hard canisters is the learned behavior of the bears: they do not expect to breach one and for the most part have learned that it is not worth it to try. Not so with the Ursack. The Ursack obviously looks and feels as if it ought to be vulnerable to a bears jaw's, and the least "taste reward" would seem to encourage that. The fact that no measurable mass is lost from the contents is not a compelling argument. A bear's olfactory senses are 1000 times more powerful than ours, and it obviously would not take a lot of molecules to make even a mouthful of kevlar pretty attractive for long enough to mash it up pretty well. Bears have ripped through enough ordinary bags to learn that they are worth attacking, and probably do not distinguish well, at first glance, between kevlar and cordura. They may not get the food, but they are going to keep trying, and that's what makes the difference.
Nor is the 1.5 inch hole argument very persuasive. That may be the standard, but it has to be pretty rare. Rare enough certainly that I have never heard of one, and the bears apparently haven't either. Porosity, however, as well as similarity to nylon bags, is inherent in the Ursack.
SO I would have to conclude that while there still may be occasional failures in hard cans, they are extremely rare, whereas the weakness of the Ursack, even short of a technical failure, is inherent: its inability to discourage attacks and protect food from mechanical damage in the event of one.
And that's a big difference. It may satisfy the criterion of not allowing the bear to actually take the food, but it seems to tend to encourage habituated behavior, which is the more important point and leads to the second point of exception.
And that is who gets to decide. The camper may pick what is best for her, but that is not necessarily the most important consideration. A decision that cannot be left to the free market is what is best for the bears, and that is usually a very different thing. If the Ursack saves my food but contributes to habituating the bear, I can't claim that consumer choice is the complete solution, can I?
