Black bears have killed 67 people in North America since 1900, so I think statistically the risk is very low [1].
I have come across black bears on several occasions while hiking in Yosemite and Sequoia national park. They have never expressed the slightest bit of interest in me. Give them plenty of space, make plenty of noise, and eventually they will wander away.
Grizzly bears, the other hand, terrify me.