I was in a fashion shop for some clothing, and a man in the same shop suddenly came to ask me if I could help him fill in a short questionnaire. Because I didn't expect such thing to happen in a fashion shop, I was surprised and said this without thinking:
what's up
Is it impolite to say what's up when someone asks you to help?
No, I don't think it's impolite. For instance:
"Excuse me, can you help me please?"
"Sure - what's up?" - seems like a polite enough way to ask what the problem is, although certainly very informal.
But as a response to someone asking you to fill out a questionnaire, it doesn't seem to make much sense. It seems like your response just needed to be yes or no at this point.
If I were greeted by anyone with "What's up?" I would immediately suspect the interrogator of hostile intent. It reeks of suspicion and hostility, or at least purveys the notion that the interrogator assumes the upper hand or a position of superiority. It may be fashionable and in vogue, but it is definitely not friendly. I would be tempted to respond with "Mind your own damned business!" Sadly a similar form, also unfriendly, used to be in fashion, was, "What's the problem?" whenever approaching the likes of a customer service situation, also nasty and unnecessary and assumes a superior status. Both convey a gross lack of respect and are not acceptable.
