Liz Phelly wrote about Spotify's mood monetization.
You should read the entire article, but here are some good quotes:
““At Spotify we have a personal relationship with over 191 million people who show us their true colors with zero filter,” reads a current advertising deck. “That’s a lot of authentic engagement with our audience: billions of data points every day across devices!”
And more succinctly:
“In a data-driven listening environment, the commodity is no longer music. The commodity is listening. The commodity is users and their moods.”
But... we all kinda knew this, right? This is how free services work. Spotify is a little different because there are users who pay for the service. Those users won't be presented with targeted advertising, but how much are you willing to bet that their data is being excluded from the data being sold to third parties? Yeah, me neither.
So what's the answer? Just dump Spotify? Honestly if Apple Music were a viable alternative I'd consider it. Apple is making a reputation out of being very conservative with user data and that might be good enough.
Or maybe the answer is to take your data back in the form of hosting your own music streaming. Plex will manage your music collection for you, and PlexAmp lets you access it from just about anywhere. A lifetime Plex Pass is about the same price as a year of Spotify Premium, although you do have to provide your own music to use Plex.
Which is probably a good thing. BandCamp is quick to point out that you listening to an album on Spotify will probably net the performer around 4¢, while buying their album on BandCamp will give them roughly 85% of whatever you paid. The performer cuts from buying MP3s from Amazon or AACs from Apple probably aren't as good as BandCamp, but probably better than Spotify.
For now I'm taking a hybrid approach. I have a hefty collection of FLAC files I bought off of BandCamp hosted on my Plex Server, but I still use services like Spotify or Amazon Prime Music to listen to new things that I'm not ready to buy yet.
And I'm quietly reminding myself that when I'm listening to Spotify, any number of advertisers are also listening to me.