I'm with Cricket and Julie- I've never been able to understand when people get possessive about clothing/style. No offense to anyone who would be upset (in fact, I'd love to hear about why you feel this way), but it's just not something that would bother me. I think that unless you've designed and made something yourself you're never going to be the *only* person with that item, so why worry about it?
I might feel this way because, when I used to live with my best friend in uni, we shared all our clothes (it was like having two closets!) and had loads of duplicates, too. I can think of at least five things off the top of my head that we both bought because we liked them so much- including jeans, shoes, a coat and several sweaters/cardis. And you know know what? I bet if we each put on all of those things today (ie, wore matching outfits) we'd still be rocking totally different "looks", because our styles are different, no matter what specific items we're wearing!