Thanks so much for your input. Having done recruiting for well over 20 years, I actually find that it does help. Not in that there is a right or wrong answer, but the logic and progression steps the candidate took to resolve the issue.
Some of the more creative answers I received included the candidate who was upset over the customer being nasty so the candidate called the police in order to get the customer in trouble (sometimes candidates are soooo honest). (Not hired)
The candidate who felt it really wasn't in her job description to handle difficult customers so she usually escalated those to her manager. (Not hired)
While I agree, some questions are throw-aways, there is also a good reason for asking some - the reason not always evident to the person being interviewed. :-)
Not answering a question is usually never a good thing. :-) I agree many worry about sounding negative, but the candidate that can turn a negative situation and tell what they learned from it gets many points from me! :-)