I've always taken issue with Cliff's recommendations. The issue he avoids is people's behavior, and the learning abilities of bears. Bears in popular areas get into food primarily because the people don't store their food correctly, especially early on the human-bear interaction sequence. People hang their food in some fashion that is easily thwarted by a bear (e.g. food hanging well in reach of a bear, or on the ground as Cliff recommends). That bear is significantly rewarded for doing this, and so the motivations of the bear are drastically increased. The bear learns that stuff sacks (e.g.) contain a lot of food, and so the bear will investigate all stuff sacks it comes across, whether through olfactory or visual stimuli. And the bear will try harder the next time it comes across human food because there is a huge reward if it's successful. Each time the bear learns something, and becomes more adept at overcoming people's marginal techniques. That's why in many heavily-used areas (the Sierras, especially) pretty drastic measures are required to keep bears away from people's food. At one time there were bear poles, or bear cables, and due to the sheer masses of people, some of whom hung their food within reach of bears, these techniques were no longer effective. With the high density of bears and people, there were lots of rewarded bears, and the bears learned some pretty extravagant techniques to obtain hung food (i.e. kamikaze bears, where the bear would jump down upon the hung food from above). There were lots of opportunities for bears to learn, and learn they did. So now bear resistant food containers are required.
In heavily used areas, bears are more adept at obtaining human food because they are presented with more opportunities, and bears learn. The higher the frequency of bear-human interactions, the greater protections are needed to prevent food conditioning (you get "smarter" bears). Cliff's recommendations are effective based on a frequency distribution/probability of people and bear interactions. Fewer interactions (e.g. less used areas by either people or bears) allow less elaborate methods for food protection. You can get away with meager food protection methods in areas where there are few bears, or where bears avoid people. Any food protection method is effective if bears aren't around (and thus keeping a clean camp is important--you don't want to draw in bears that would otherwise stay away). If a bear stumbles across one of Cliff's stashed bags, it's going to investigate and probably eat everything. And then it learns a) food bags have good stuff, and b) maybe there is more out there. Even if the bear doesn't find the other stashed bag during Cliff's stay, it increases the chance the bear will find a bag if the next group stays there. Bears learn, and with more opportunity, the quicker they learn. Cliff's techniques won't work in heavily used areas--bears associate camps/people with food, and they'll investigate. In more remote/less used areas, his techniques might work, simply due to the probability of interaction between bears and people and the presence of naive bears.
I could go on and on, but you get the idea.
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