TOD: I don't have a specific experience in mind that's worth relating, but I think there's just about nothing like having a lousy restaurant experience -- and feeling ripped off in the process.
I think most of these times -- probably not all, but most of them -- have been something I could sense upon entering the jernt. Sometimes I've been with someone for some special occasion or something, and have no say about the venue. Those times, you're just stuck. But other times, I'll sense it but go immediately into denial, telling myself I'm going to make the best of it, choose what I eat with great care, etc., etc., etc., but "best of it" just doesn't happen and the whole experience sucks, and you're left saying "that's one (hour, meal, expense, whatever) that I'll never get back." I think restaurants are kind of unique in having the power to do this to you.