I may have posted this before, but look at facebook and their partnership with thousands of companies. You go to almost any website and it puts a FB tag on you. It is an anonymous tag at first UNTIL you log into your FB account. Once you do that, every website you visited (that puts a FB tag on) since you last logged into FB has now transferred all your search items from that site to FB. FB in turns uses that tag and your history to market to you. Yup.... FB knows more than just what you post on their website, it knows the vast majority of what you do online.