Holidays Shopping question?

Do stores around you ask for your phone number when you go in to purchase things? And if so, do the check-out people get noticeably less friendly when you nicely refuse to give it to them, since you don't need anyone else having your phone number? I had a woman act like I had personally insulted her when I said, "No, that's OK, I'd prefer you don't have my phone number." I think in the future, I'll just answer with, "Aww, that's sweet of you, but I'm already married. Thanks!" :P