I've noticed the same thing. A guy I see kiting every now and again has a blue heeler and it barks continuously, hassles people for food, digs and showers you in sand as you stand chatting - and he is oblivious to it all....I imagine if I told him his dog was pi**ing me off, he would be mortified...its like some people & their kids - they get immune to it and just dont see it happening - or have grown tired of trying to modify the behaviour and have given up.

Next time - follow the dog owner and when he stops, piss on his leg - or even better, start humping it. That's guaranteed to get their attention.