I’ve done it myself a zillion times: after you swipe your credit card and the cashier bags your new jeans, she asks you for your ZIP code, and you ... tell her! Kind of annoying, but no big deal, right? Well, turns out it actually can be a big deal, and it’s definitely not a good idea.
I realize that I’ve never really thought about WHY stores want that information; I’m more just focused on wanting to get done and OUT (I love new clothes but I hate shopping!). I guess if I gave it any thought, I figured they were interested in knowing where people came from to shop in certain locations. Well, demographics do play a part in why they collect that info, but there’s a lot more to it than that.