There’s an old expression: if you’re not paying for the product, you are the product. This is broadly understood by many people to apply to social media and they’re right. If you’re enjoying Facebook’s service, great. If you think you’re getting it for nothing, you’re kidding yourself. Facebook is tracking what you do on its site and when you hit a “like” button on someone else’s site.
A number of online facilities are starting to become available not so much to fight this as to help people understand what they’re handing over. https://nakedsecurity.sophos.com/2017/02/23/how-much-does-facebook-really-know-about-you-and-is-it-right/