What are the chances that someone else on the subway is listening to the exact same song on his/her iPod at the exact same time with those millions of iPods and millions of songs. Imagine the surprise when you would notice that. Suddenly you see the realization in the other person eyes. Who knows you might start singing at the same time. Then again. Would you notice? You can see the earbuds but with the blank faces its hard to tell which song one listens to. So scratch that thought. People do not know that they are listening to the same song. But that's good.