While I don't carry, I've seen first hand what a shot of bear spray will do to a human. Not just a garden variety squirt can with mace. The stuff capable of stopping a charging grizz is much stronger, pepper based, and some are capable of shooting a targeted fog at a range of 30 feet. I was on a fishing trip in Alaska and a guide accidentally discharged a can that only gave him a glancing dose. He was in instant agony, screaming and clawing at his face. I can't imagine what a full targeted dose might do to some tweaker trying to rob a car wash owner of his cash. Of course, you'll probably end up having to shoot him with actual bullets when he makes bail and comes back after you for revenge.