My story:
On fine day, I'm hiking quietly and ''Merde!'', I spook a bear sow and her cub!
They run, fortunately for my skin.
30 min later, going up a trail, I'm ringing my bear-bell as loud as I can and what do I see at the top of the hill? Our young cub, at 20ft max, sniffing some bear food, not even aware I'm there!
The little bugger is either deaf, stupid or simply not able to hear the bell's frequency.
I clapped my hands, spoke to it dirty in French and it ran.
Morale of the story: Don't rely on bear-bells.
A non-scientific test published in Backpacker Magazine demonstrate that clapping your hands, breaking branches and singing is better.
Singing in French also attract women...
I think the best info on bear safety is the DVD : Staying safe in Bear Country.
http://www.bearsmart.com/moreStuff/StayingSafeScript.pdfPS : As for the predictability of bears, well, they're more predictable than humans. Ha!