Facebook has more than 500 million active users. Every link you click, every post you like, every piece of information you share with your friends on the site is also shared with Facebook — and their advertisers. Facebook isn't the only Internet company tracking you. Google, Yahoo News and plenty of other sites do the same. But how are these companies using your information? As the Internet becomes the primary way we get our news and understand our world, how might this filtering affect our world view? In other words, what aren't we seeing?
Eli Pariser is the author of "The Filter Bubble" and the former Executive Director of MoveOn.org.