There are extremes, and twice since I've lived here in small-town-midwest where everyone is almost always infalliably polite, I've seen two large groups (years apart, in different towns) eat over 3/4 of their dinner, drink copious amounts, and try to walk out w/o paying, insisting that the (consumed) meal was unacceptable. Ironically, both groups were biker groups. I say IRONICALLY because before here I lived for six years in the Daytona Beach area, where there are two major bike weeks a year (i.e., more bikers in any given month than both these towns ever see, put together), and everyone loves to see them come, and never, and I do mean NEVER seen that behavior. Yet both towns (and both restaurants) still maintain that they love bikers and welcome them. There are always people who will try to get over on a restaurant. If you're returning food (or a wine or drink), you'd better darned well not eat most of it before hand.