"I agree the collapsible option would be heavier and a little more expensive but I don't think for one minute it would be more complex or a weak link. If it was then it couldn't be approved."
It could not help but be more complex and a weak link to boot. And as much as I have gone through with Bear Vaults over the years I see this idea never coming to fruition.
"I see everyone's concerns but 3-4oz is a few gulps of water."
Not to beat a dead horse, but 4 oz more puts you close to the weight of existing bear cans, lower priced and undoubtedly structurally more sound.
"Think how nice it would be to have a canister that adjusted to how much food you were carrying and on long hikes would get smaller and easier to pack as the days went on."
Yes, that is a nice thought, but as we had to bring a pack that would hold it in the first place it won’t help that much in my experience. (I use them a lot.) When mine get to a point there is space (if I even carry my food in it in the first place) I just start storing stuff in it.
Between Dave and I we have bought 5 Bear Vaults and one Bear Keg over the years. I liked the weight of the BV's but I am so happy I switched to the more expensive and lighter Bearikades. At least that way I don’t get told every year or two that my can is not allowed when I show up to pick up my permit.
I said I would be interested in one and am, but I really doubt a collapsible can will get approval, and I would not trust it anyway. Do you know how many people cannot adjust their trekking poles…?