Quite a few times.
Around 6-8 years ago they were taking all the trouble bears from the national parks/touristy areas in the mountains and relocating them to an area where I hunt/camp and stuff. Went out with my grandpa just driving around farmer's fields and shit, counted at least 30 different bears within a pretty small area size. We stopped in this one field where bears had eaten quite a bit of this farmer's crop and got out of the truck to walk around and check it out, we get about a good 10-20 feet from the vehicle and a bear that was eating which we didn't know was there stood up right in front of us like a couple feet away and just stared at us while it was munching away. We almost turned and ran away out of instinct but did the right thing and slowly backed away. I wasn't really worried that time because it was a black bear and it was more worried about eating than us.
Last time like 2-3 years ago we were taking a trail next to a farmers field that goes to a power line on crown land where you can hunt and it's a tight/narrow trail where you can't just turn around and about mid way into the trail we run into a big brown bear that wasn't moving out of the way. Bastard wasn't scared at all and just started slowly walking towards us and we're in a side by side without any windows or doors protecting us. Had to throw it in reverse and back out of there while this big ass bear's walking towards us and the side by side almost got stuck in the mud. I just kept my gun trained on it the whole time in case it got too close or started to run/sprint towards us or something.
Good way to get your heart going, that's for sure. Don't fuck around with brown bears though, they're way bigger than black bears and they're not easy to scare away. Black bears are real pussies compared to them.