Someone who worked with me one time said they had worked at a fast food place and they told me customers there are the nastiest, meanest customers, and will literally throw food on a semi-regular basis. It was in the context of my telling them that out of all the places I've worked, that grocery store customers seem to be the worst, but she said fast food customers are the worst. She said if any small thing is wrong on their order they will often cuss and scream and throw food. Makes me really glad to be an overnight worker putting stock out, I don't have to deal with customers at all in any form most of the time now.