What about when 2 of these people meet in an aisle and start talking, while blocking anyway around them entirely. And then they give you some dirty look when they see you standing there, looking rather annoyed, after they have ignored your polite 'excuse me'.
I think I will start bringing a cattle prod to the grocery store from now on. The sense of satisfaction I would gain from jolting people would be heavenly. People would then fear and just move out of the way when I go places.
Hmm, I think I might have stumbled upon a great idea. If any of you hear a news story about this, you will have a face to put to the name at least