Seriously, how hard is it to back out of a parking spot? I'm all for taking your time if no one's waiting, but when you see a line of cars behind the car waiting for your spot, please stop being a self-centered asshole and vacate in a timely fashion.
My recently departed grandfather :( used to call these people "pilots," because, he said, it's like they have a laundry list of gauges to check before takeoff.
Don't be a pilot . . . unless you're actually flying my plane.