Some great info on the subject can be found in "Future Crimes" - Marc Goodman . Everyone should give it a read.
An excerpt from the book.
>Facebook is by far the largest social network in the world. It has succeeded by getting people to talk about themselves in ways never previously imagined. Sexual orientation, relationship status, schools attended, family tree, lists of friends, age, gender, e-mail addresses, place of birth, news interests, work history, catalogs of favorite things, religion, political affiliation, purchases, photographs, and videos—Facebook is a marketer’s dream. Advertisers know every last intimate detail about a Facebook user’s life and can thus market to him or her with extreme precision based upon the social graph Facebook has generated.
Moreover, Facebook created a variety of innovations that allow it to track users across the entirety of the Web, including via its omnipresent Like button. You’ve been trained to click on the cute little blue thumbs-up button to express your support for a particular idea, status update, or photograph; after all, it’s the polite thing to do. Your friends see that you support their message, but what neither of you see is what happens with the data generated with each and every Like—data that are captured, dissected, and sold to marketers and data brokers around the world. When you use Facebook’s ubiquitous log-in credentials to visit other sites on the Web, such as Spotify and Pandora, Facebook’s data-mining engine is crunching your preferences for Lady Gaga over Blake Shelton, just as it is tracking all the Web sites you visit with the Facebook icon on them (even if you don’t log in).
In case you aren’t sharing enough, Facebook is happy to create new rules and regulations to force you to share more, as it did in 2012 when it instituted its mandatory timeline “feature.” The change provided advertisers a dynamic, ever-updating window into your life’s interests at any moment in time and more fodder for Facebook to sell to advertisers.Facebook is building a new data center in Ft Worth, TX. If you saw the size of it you would be terrified. It makes a Walmart Distribution Center look small.