It's an interesting symmetry that's like cyclical Muzak (now Mood Media, iHeartRadio for business, etc..) On one hand you have human- or machine-generated playlists of background music designed to put you in a mood (usually for monetization, but sometimes to study, work, exercise, fall asleep, etc.) while on the other hand you have reverse-engineered behavioral modeling based on what you're listening to (presumably also for monetization.)