I am very surprised that most people do not know this has been going on. And FB is not the worst with data. Google does not consider its users to be customers, but rather the commodity. Google's inception was based upon selling data it gets from its users. Not much different than cigarette companies, cola companies, clothing companies creating items to target specific groups of people. It is that Google guys discovered the algorithms for tracking people's habits and figuring out how to use it like other retail creators do, only on the internet.
Have you ever gone to a web site, looked at an item, say a drill press or vac system or something else, then the next day visiting on another web site, or even FB, and you get ads for vacs or drill presses or tools? Yep, tracking. This information is VALUABLE to tool companies, so you become the commodity and companies such as Google and FB make money off of your likes. AND your political preferences are targeted and sold too. Been going on a long time.
I lived overseas from the US for over 25 years in a safe country, but I had coworkers that lived in some very security sensitive countries; back in the mid to late 90's, they were tracked via their internet use, even with VPN usage. Co-workers who didn't take security seriously wound up in trouble and kicked out of the country. That was 20 years ago.
Your information is out there. Even if you don't mind people knowing it, there are companies that want to know it and use it to their advantages and will. Casual but regular FB use, casual but regular Google search use provides enough data to build a psychological profile of you. And this is my issue with using Google search - they keep records of your search from the first time you used them. About 3 or 4 years ago, I found out how to look at my Google search data. WOW, they had my "search" data back in Japan in the early 2000's. Google got into the smartphone business to track data usage and sell it. That is why Google did not charge for the android OS. Give it away to track data of its users. FB is just the tip of the iceberg.