Well maybe for your experience "All in told I can only think of a hand full of canisters failing - and in every case it was due to a lid not being put on right!", however, Bearvault has experienced numerous failures of their past products where the lids were put on correctly. That is why Bearvault is now producing the BV500 and not the BV100, they are continually having to change their design because of the failures of products that were used properly and in every case, at least one bear has "learned" how to get into a Bearvault that had the lid put on correctly. For example, a bear in the Rae Lakes area of the Sierra Nevada Mtns figured out that by sitting his 400 lbs on the BV300 (and previous models) and low and behold, the correctly closed lid would just pop right off. Hence the new canister and lid design starting with the BV400. Here's a quote from the BV website:
"Currently hikers to the Rae Lakes drainage basin Rae Lakes drainage basin in Kings Canyon National Park cannot use the following BearVault bear canister models: BV110B, BV200, BV250 or BV300. There were 8 break-ins during the summer of 2005 and until more experience is gathered this summer, the use of the above models is not allowed in this area. There are currently no restrictions on the use of these model BearVaults elsewhere in SIBBG controlled areas- they can be used throughout the Sierras and all other locations."
Although it's not fully acknowledged there, there is other info available on the internet regarding these breakins and I think that the redesign and complete retooling for manufacturing is BV's acknowledgement of the failure of their products. In heavily used problem areas it's only a matter of time before bears figure out the BearVault system. Here's the latest from BV on the current situation in the Dacks:
"In response to this a new lid was developed for 2008 which had two snaps on the lid which both required being pressed in sequentially- this is the model BV450/500. Testing was conducted during June and July 2008 at Marcy Dam and Lake Colden. We now have the test results. Surprisingly, the bear(s) pressed in the first snap with its incisor, rotated the lid and then pressed in the 2nd snap with its incisor and opened the lid."
Doesn't sound like operator error to me. If one bear can figure it out, eventually others will too, especially in areas where there are bears already habituated to human food and are willing to try anything. This is why even a "proper" hang in certain areas does not work. For example, Bears in Yosemite have been seen using the kamakazee technique for obtaining food from a "proper" hang that is the correct height and distance away from the tree. In this technique, the bear climbs to a point on the tree above the hang branch and then dives off into the hang branch below, usually effectively breaking the branch and sending the "proper" hang to the ground where he/she and the fellow gang of bears make short work of it.
so in summary, no matter what you do with your food, if you're in an area that bears don't frequent, it probably won't matter, you won't have a problem (with bears anyway) if you leave a bag out on the ground. However, if you're in a place like the Dacks, or parts of Yosemite, or Rae Lakes, you may lose your food even in a correctly closed BV. I would like to say that I have never heard of a successful breakin by a bear to a Bearikade or or Garcia canister. If anyone has any knowledge of this, let me know.