I've had three close encounters with black bears over the last forty years - one in the Shenandoah, one in the Maryland Alleghenies, and one out in the West. From all the other people I've talked to who have had similar encounters, we all seem to agree on a few things. One is that bear canisters work, but be sure you get it down in the ground or under a rock with a can or pot on top to let you know the bear is after it. The only time I would bring the canister in the tent with me is if I'm on a slope and couldn't get the canister anchored any other way - I had a friend hear his canister take a 1000-foot trip down the mountain one night. Second, if you have the food, the bear isn't going to fight you for it. If the food is hanging in the air, it's fair game, and the bear will have to be persuaded to leave, but it might come back. And third, if the bear has the food, it will bluff or fight to keep it, so you might as well concede the issue. The PCT method of bear bagging has a lot going for it - people should learn it and practice in the park or their backyards before they hit the trail.