If you’re one of the site’s 2.6 billion users, Facebook’s operators know where you are all the time, whether you’re logged on or not. They know what you’re buying, even if you’re in a brick-and-mortar shop. They scan photos you upload for biometrics. They mine your data and sell it to advertisers, but they won’t say how much of it, only that it’s a small amount, promise.
Facebook’s not the product. We are.
When you use Facebook, you're giving all of your information to the kind of Techno-Nazis who want to control you. And they'll end up doing so. Their software is designed to control you, so that they can get what they want from you.
Delete your Facebook account. It's not worth it.