Hey Conan -
Here’s two stories from Alaska & 1 from the Yukon. Enjoy!
Alaska: In the summer of '95 my buddy ken (‘katz’ trailname) and I traveled all over Alaska backpacking in a lot of the cool areas. At one point on this trip we took the ferry from Valdez to Whittier and were told by locals to backpack over Portage Pass to Portage Lake, which has a beautiful black sand beach and an incredible glacier which calves ice burgs into the lake. At the Pass I was way ahead of ken and decided to wait for him. I sunbathed on a large granite slab for probably a half hour. The wind was blowing from the North that day. When I got up to look back down the north side of the Pass to see if Ken was coming, I was shocked to see a black bear not more than 4 feet away! He was as shocked as I was, as he could not see me or smell me from the other side of the rock. I did not know what to do - we were both terrified and frozen in our tracks so to speak. I could see the fear in his eyes and I’m sure he knew I was petrified as well…
After a LONG period of stalemate (45 seconds?), the bear slowly backed off facing me and when he was about 30 feet away he turned and ran for his life. Since this incident, I have always done exactly what he did - especially if I run into a mom with cubs.
That same month while I was in Wrangell St. Elias N.P. Ken and I took the aerial tram (two person aluminum zip line) over a ranging glacier melt river to McCarthy. We then mountain biked up to the Kennecott copper mine ruins near Root Glacier. This was in the middle of the night, but since we were close to the Arctic Circle near the Summer Solstice, there was plenty of twilight. En route to kennecott, when we rounded a hairpin turn on the jeep road, we ran into a huge Brown bear (Grizzlies are a type of Brown Bear. Alaskan Brown bears can weigh as much as 1,500 pounds!). It was much too close to be comfortable for us and the bear - about 20 feet. (animals, like people seem to have a boundary zone - inside that zone they are threatened) The bear stood up (he was probably 9 to 10 feet tall erect & his head was the size of a hood of small car!) and rocked his head back and forth sniffing the air. I instinctively knew he was determining what kind of threat we posed. In the mean time I got off my bike and prepared to throw it into the charging bear if that happened and then run for my life! I am well aware that you are never supposed to run from a Grizzly or Brown Bear and had recently been lectured on this by a Ranger at the Park HQ, but there was no way that I was going to lie down on the ground and take even a minor mauling by that monster! And besides, Ken is a short, slow, rather fat middle aged guy (like ‘katz’ in Bryson’s book - thus the trailname) so I figured my chances were better than fifty/fifty
Thank God the bear got down on all fours, took a few steps into the brush and let us go by him.
The final encounter happened south of Dawson in the Yukon or northern B.C. We were heading back to the ALCAN Hwy and I noticed a tiny little black bear cub about 10 feet up a tree on the left side of a remote section of highway. We stopped the van and saw mama bear about 100 yards into a field to the right of the highway. I realized that this was the perfect opportunity to study the reaction of a mama bear with a cub. I got out of the van and stood in the road between the cub and mom. I only had about ten feet to get to the van (an old Ford E350 with the heavy duty metal exterior) if I had to make an escape. The mama kept calling the cub and the cub kept whining back from the tree. (I stood in the road not moving) After maybe 5 minutes, the cub shimmied down the tree and started walking towards mama (who was directly beyond me about 100 yards) The cub made no attempt to go around me, but literally almost stepped on my toes. I stood motionless watching the mom intently. When the cub got within maybe 5 feet of me, the mamas demeanor suddenly changed - her hair raised up and she charged like a vicious dog. I sprinted to the van. It appeared she was running at least 35MPH. I got in the van with a couple seconds to spare and she nearly rammed the van with her head. (the van was idling in case we had to floor it) She looked at me through the windows, growled ferociously, looked over to her cub and then casually walked away with the cub as if nothing had happened. The charge looked like an instinctive reaction more than a rational pre-meditated action.
After these encounters, I’ve always been wary of a mom with cubs, I never ever try to frighten a bear, and I always keep my distance. In my personal experience, nearly every bear that I have run into is afraid of humans and just wants to be left alone. The very few ‘camp’ bears that are considered ‘bad’ bears are just looking for some free food - which unfortunately they have been trained to do by careless humans.
Of course, I’m not by any means a bear expert - these are just my observations. 
Happy Trails,
freebird
freebird