Having been around bears in the wilderness a lot, I just don't understand peoples paranoia about them. And I disagree that Grizzlies are more aggressive then Blacks, that has not been my experience at all, and I've seen no real data to that effect.
Gyrene.. you talk about when you accidentally startle a bear, and yes, you are right that is when they will attack, if they attack. But just as often, probably more often, when you startle a bear it will just run away in a big hurry. Besides with the incredible hearing and smell that bears have, it is pretty dang hard for a clumsy human to sneak up on one. As for the mountain biker story, sounds like they had some crappy spray, it is not all created equal, I spring for the expensive (about $70-$80 a can) stuff, or maybe it was old, you should replace it every couple years because it does loose potency over time. But it did apparently keep the bear at bay long enough for him to loose his nerve and leave. Who knows what would have happened if they had taken a pot shot at it with a handgun, it is very possible in that case that they may have just wounded it enough to piss it off and been in really bad shape. So... I'm not convinced it would have ended any better with a handgun instead of spray.
I did manage to startle a black bear in the Winds one day, we came over a rise and out of the trees into a small lake basin from downwind and he was about 50-70 feet in front of us, in the middle of taking a dump
. He froze and stared at us for a few seconds, I kept my head down and we slowly backed away (while getting the camera out). After staring at us for several seconds he turned and ran off. The pile of scat was still steaming when I came back to it.
To put it in perspective, according to Wikipedia (which could be wrong, but is usually right) there where 26 fatal bear attacks in the North America from 2000 to 2010.
Yet in the decade from 1998 to 2008 there where 449 deaths from lightning strikes just in the USA, and thousands die every year from hypothermia, or drowning in the backcountry.
I'm just saying if something happens that is going to cause your death in the backcountry, odds are that it won't be from a bear attack. I worry more about weather, or falling and breaking a femur, or falling in a river when fording, or mistaking death kamas for wild onions (not really but it has happened), killing me on a trip then I do bears.