A Facebook reality check from Michal Kosinski, who has a lot of relevant experience in the domain; e.g., see The Data That Turned the World Upside Down | Motherboard (a January 2017 overview of how Kasinki's research approach was leveraged by Cambridge Analytica)
"Facebook would even let advertisers target you based on facts that you may not be aware of, such as that you are a close friend of a soccer fan or of someone who got recently engaged. In a recent study we published, my colleagues and I discovered that advertisers can target users based on their intimate psychological traits, such as personality. If you can think of an important personal characteristic, there’s a good chance it’s targetable on Facebook. Through this ad-targeting system, Facebook discloses facts about you to advertisers, in exchange for money, every time you click on an ad. I’d call that “selling data,” and I bet that you would, too.Congress May Have Fallen for Facebook’s Trap, but You Don’t Have To | NYT
But Facebook is extremely clever at dodging this issue. When the company argues that it is not selling data, but rather selling targeted advertising, it’s luring you into a semantic trap, encouraging you to imagine that the only way of selling data is to send advertisers a file filled with user information. Congress may have fallen for this trap set up by Mr. Zuckerberg, but that doesn’t mean you have to. The fact that your data is not disclosed in an Excel spreadsheet but through a click on a targeted ad is irrelevant. Data still changes hands and goes to the advertiser."