Ironically, the popular media has historically been the one of the largest sources of consumer data for ages through magazine subscriptions. They sell their data to brokers like Axciom (and many others) who package it and literally sell it for cash for anywhere from a few pennies per record on up depending on what features you want. Just addresses, addresses and phone numbers, number of cars owned, family make-up, age, etc.

Facebook is honestly quite humane in comparison. No one knows this stuff exists except direct marketers, which is why it doesn't get any attention.

Facebook gets much larger quantities of mundane information like you clicked on a news article, or you went on vacation to a certain place, etc. It also has social graph information that data brokers don't typically have like "is close friends with a woman with an upcoming birthday." That is a real ad targeting example you can do on Facebook.

Sure. But if you run an ad targeting certain demographics, and then get click-throughs on those ads can you then make the connection between users/demographics?

I also do find it interesting that app developers get access to more information than the paying customers themselves.

I'm at a loss to understand why people keep using the words "sell data" in this way. It's a weird way to use the word and inconsistent with how it's used in other situations.

Would you also say a pizza delivery driver sells their car? It's a resource that they use while providing a service but they retain possession of the car. Most people wouldn't describe that with the word "sell", so why does the definition shift when it comes to user data?