I can't help thinking that this problem would have been solved more amenably by hiring an overly eager teenager to relentlessly advertise to the lingering customers.

"Can I get you another coffee, ma'am? Would you like to try our french fries today, sir? How about something off of our value menu?"

If you throw a cop in my face, I'm more inclined to be stubborn, but nothing makes me want to vacate a place of business quite so much as an annoying salesman.