"Facebook is a great utility if you want to stay in touch with friends and family, share photos, and see what other people are up to in their lives.It's free to use, of course, but that doesn't mean it comes without a price. If you're using Facebook, you're giving the company a ton of information about yourself which it is selling to advertisers in one form or another.
And most people forget that when they download or sign up for an app
or website using their Facebook login, that they're giving those
companies a direct look into their Facebook profiles and some of their
personal data. That can often include your email address and phone
number, but frequently also your current location."
Great how-to article by Jim Edwards on Business Insider. See full article here: