Did you forget to tip your waiter/waitress? Hmm...?
Have you been rude to waitstaff? Do you not bother to tip them? Sometimes they can get quite nasty, though you won't always notice. While I wouldn't do many of the stunts involved here, I do have a certain sympathy as I used to live off of my tips while I went to college. I'm sure that some of the stories have been "embellished", but I worked in the industry long enough to know that many of those have a ring of truth to them.