Someone said, "we decided to carry bear canisters, not because we were worried about encountering bears, but because we were worried about encountering rangers". A sad commentary certainly, but it does boil down to this in many ways.
I must note that in many areas (see discussion below) of the Sierra, canisters are not mandatory, although some measure to keep food from the bears is (and rightly so). On my last two trips when I dutifully carried a canister, I could have opted not to. (Not only was one not mandatory, but I never encountered bears or rangers). Now that I have an Ursack, that will be my chosen mode in such areas. Regulations could change at any time and/or you could encounter a ranger who has his own ideas about the rules.
You can read the 2009 food storage guidelines statement from Sequoia and Kings Canyon parks.
Or just forget it. Probably the source you have been reading is giving you out of date information. Bears in the California Sierra figured out this system a long time ago, so you are forced to deal with a ....
The drawbacks are the weight, the expense (and/or hassle) of getting your hands on one, and its peculiar bulky barrel-like shape (it makes a so-so chair to sit on). You also need some kind of tool (I carry a couple of quarters) to work the latches.
An issue with any canister is that it can be a real trick to get all of your food for a long trip crammed into it. This has led to a fairly common situation where people are carrying a canister, but have some of their food outside the canister, and bears raid their camp and get a "food reward" anyway. If all of the food isn't in the canister, there is little point in having one at all (from the point of view of changing the behavior of the bears). Most likely these people are just starting a trip and hoping they get lucky with the bears until after a day or two they are able to fit everything in.
I have also heard of bold bears in Yosemite pushing right past people at a daytime rest stop to grab packs or attempt canisters.
The Bear Vault is a competitor to the Garcia. The BV500 holds 7 days of food and weighs 2 pounds 9 ounces (no better than the Garcia). It looks like a giant heavy duty clear plastic jar. I see them on sale for $70, about the same as the Garcia. The lid works like a child proof medicine bottle, and certain bears in the Adirondacks have learned how to open them
The fully approved cadillac option is the Bearikade Canister from Wild Ideas. It is made from carbon fiber composite and aluminum. A "Weekender" costs $225 and weighs 1 pound 15 ounces. (A lot of money to save 9 ounces!) It is 9 inch diameter, and 10 inch long 650 cubic inches. The "Expedition" is 900 ci and $275 (14 inch long), 2 lb 5 oz, There is a small version called a "Scout" (8 inch long, 500 ci, $195, 1.75 pounds). Wild Ideas sells and rents these.
The Weekender can be rented online for $5 per day for the first 3 days, then $2.50 per day, plus $10 shipping. (i.e for a 6 day trip, 15 + 7.5 + 10 = $32.50)
A much more attractive option with some issues is ...
Ursack capacity is 650 cubic inches, which is just a bit more than the 614 cubic inches of the Garcia, but without the bulk and weight. (There used to be a big version called the Ursack Major with 1200 cubic inch capacity, but it has been discontinued.)
Ignoring all of the legal issues, it takes some care to use the ursack properly. Use an odor barrier plastic bag inside. The opening must be closed with absolutely no gap, and the knot tied in such a way as to keep it closed. Part of the ursack design intends for it to be anchored to a tree, large rock, or some immovable object (in this way, a bears efforts will tend to pull the opening closed). Park authorities will tell you not to do this, because they are concerned about damage to trees by the bears efforts.
Mice or other small animals with tiny sharp teeth have been able to damage an ursack. Marmots are apparently stopped by an Ursack.
The ursack has the option of an aluminum insert. I am not entirely clear on this, certainly it will help keep your food from being smashed to powder. I am a bit skeptical about having a piece of metal with sharp corners inside the sack. At one time it was what was required to get the agencies to smile upon you, and perhaps still is (or will be if the ursack again gets approval). Apparently the "thinking" of those in power is that once your food is all smashed, you will (you being a lazy dog) dump it out on the ground to lighten your load and high-tail it for the trailhead. The last thing I would do certainly, but it shows just how these people think about those that they serve: we are idiots who need to be managed.
If your aim is to avoid hauling a canister around, you should study a map of the Sierra and figure out places where a literal canister is not required and plan trips to those places. Another option is to hike like the wind to get through a canister mandatory zone and camp legally with an ursack. (Impossible if you are talking about Yosemite Park).
There is a dandy map of where canisters are required which you can find by rummaging around at the Sierra Wild Bear site.
I made a copy of the Sierra Food Storage Map on 1-20-2010 from the above site, and offer it to you here (the map was dated 8-26-2009, but has not been updated as of 7-2011), but you really should visit the real site via the link above in case policies change and the map gets revised.
A quick verbal description of the canister mandatory areas is as follows:
It turns out that a canister has not been required in the places I have done my backpack trips (and dutifully carried one). When asked, the rangers will of course say (and they indeed did) that a canister is a "recommended" (no doubt it is a good idea) and should be taken. Bears are less likely to wander around above timberline (where I usually prefer to camp), but it is always possible, and they have most certainly figured out certain "high use" areas (both above and below timberline) where there are lots of people and a good chance of finding unsecured food.
Of course this can all change (and likely will) at any time as the agencies involved get new ideas and as new bear incidents get their attention.
During the times of highest use, these are areas that I would generally choose to avoid in any event. However these are beautiful areas that I would be pleased to visit in off-season, such as the fall when the crowds have significantly thinned out.
Uncle Tom's hiking pages / email@example.com