On the train, I've often been sitting in my seat knitting when I notice the flash of a long, thin white thing out of the corner of my eye. My first thought is usually, "Cool! Someone else is knitting on the train." Then I actually look over, take a moment to process what I'm seeing, and realize that it is not, in fact, white yarn at all. It is a pair of iPod earbuds.
You would think that I would have made this mistake only once. In fact, it happens nearly every time someone pulls an iPod out of their bag. I almost was at the point of asking one of these folks what they were knitting before realizing my error.