I have had different experiences. I run into several bears every year. Habituated black bears are not that easy to run off, however, you need not carry weapons! I have had many bear encounters, some really up close! Treat EVERY bear encounter as a potential problem. If on the trail or off-trail, detour around them and be careful not to appear threatning (I always talk to them calmly while I walk by and do not look back at them). Look around to see if a cub is nearby. Getting between mom and cub is not good. In camp, just being clean is not enough in areas of habituated bears. That is why bear cannisters are REQUIRED in much of the Sierra. I have had a bear roll around my bear cannister then come and poke his nose inside the tent! Repeated attempts at running him off with noise failed. I had to get out of the tent and literally run him off screaming and waving with my trekking poles. Throwing rocks sometimes helps. The minute a bear comes into your campsite, make it very clear to him that he is NOT welcome! If your food is not protected, he will get it. Do not try to take it back. By the way, bear spray is not legal in some national parks.