You might think yourself a unique soul, but thrown into a data pool of the tens of millions of users of an online service, your behavior is going to sync up with somebody else's at least some of the time. (Sorry, Quixote!) On Spotify, this means you're going to be listening to songs in sync with someone else.
That video artist whose software grabbed pictures of Apple Store computer users? He's been tracked down by Apple and raided by the Feds. He had to see this coming.
Kyle McDonald, an artist, installed software that would grab pictures of people's faces while they were using a public computer. It's sorta creepy and invasive but also gives a unique look at how weird you look when you're on the computer.