The bear cannister vs hanging choice is a good example of the typical trade-offs you have to consider when trying to go lighter. I totally agree bear cannisters are handy. You "pay" for the weight savings when hanging- cost is about 15 minutes to properly hang (and sometimes up to 30 minutes to find a campsite that will work)and the annoyance when once hung, you forgot to put something inside! The "cost" of the bear can is the extra weight. An additional "cost" of the bear can, for me, is the bulk. I actually have to use a heavier (bigger) pack when I take the bear can. Because I am small, and my packs are small, I have to put the bear can in vertically inside the pack. this takes up nearly all the room and makes balancing the pack weight very difficult. It also makes the pack "stiff" and uncomfortable unless the pack has a good rigid curve to the side next to your back (cannot carry the bear can in a frameless pack). If your pack is men's large, you can put the can in horizontally - a much better method. So not only does the can add the weight of the can, I also have extra weight of the pack, and the extra "feel" of heaviness due to not being able to get the weight close enough to my center of gravity. This is why I use my Ursack whenever it is legal. True, it is not 100% bear-proof, but it packs so much better and weighs 8 oz. There is always a trad-off. Each of us will choose what we are willing to gain or loose.
You can save ounces also by choosing lighter and sacraficing sturdiness. The heavier plastic bag for a liner will last longer, so is more cost effective. I, however, rather take the lighter plastic bag and just buy a new one for each trip.