There are no negative attributes to this behavior, except for the obvious sanitary concerns you might have. Dogs may lick people as a signal of submission to more dominant "pack members", and licking of the ears specifically is supposed to be more of an indication of this. Or they may lick because they know they are not allowed to bite and want to occupy their mouths. More often than not, however, licking is a sign of affection and closeness. If you ever watch two dogs from the same home relaxing, they will spend hours grooming each other in a loving manner by licking.