It’s interesting how this has become a concern. In the MP3 era, pretty much every obsessive music fan I knew IRL was signed up to Last.fm and scrobbling (i.e. uploading a recording of listening) every track that was played on their MP3 player. You could then compare your listening to your friends’, meet new people in your town with the same tastes, etc. There were no concerns back then about privacy, because no companies had yet so clearly abused it. But considering how Last.fm has always struggled with monetizing the data it does get, even now the site sparks few concerns.

(For those whose privacy concerns would prevent them from using Last.fm to keep track of their music listening over time, there is Libre.fm. However, all it is good for is keeping personal records, not socializing with many other listeners.)