AvatarJamie KaskiwHow To Discover Everything Facebook Knows About Youverified_publisherBusiness Insider - Julie BortThere's an unwritten agreement every user makes with Facebook when they sign up for the service. Facebook is free and fun to use, but it will track your activity and content to help its advertisers. You can't opt out of ads on Facebook without opting out of Facebook itself. But you can do a lot to …