After about 55 trips to the BWCA and Quetico I have never seen a bear at my camp.  I have seen a yearling swimming across Quetico Lake and I have seen a bear at the BH parking lot.  The best way to avoid bears is to go to campsites which are not used very often.  It may not be a direct correlation, but the more a campsite is used the higher the probability of encountering a bear.  It is no different than if you catch fish in a certain spot you will return to that spot again.