Often someone has something very similar to mine (usually the same style in a different color). What's really odd, tho, is when a kid shows up with the same shirt I have! I don't mean the school tshirts. Last week a girl came outside wearing the same tshirt I had just bought. In fact, I almost wore mine that day.
It used to happen quite often at my old company. We did have a lot of logo'd items, so that was a given. But one woman had a nearly identical black shirt with small white polka-dots, and a sage green blouse that was almost identical to one of mine. More often than not, we both wore the matching shirts on the same days. We just told people who commented that we call each other every morning and coordinate our outfits!
I met a friend who was visiting from Tennessee with a large group a few weeks ago and we were both wearing almost identical outfits (same sweater, style of jewelry, jeans, flat brown shoes). We laughed and took a lot of pictures.