Diversity in the information people see and attend to can help people and groups make better decisions, can help people learn and correct inaccurate beliefs, and can help people see ideas with which they do not agree as legitimate. Media policy in the United States has long had a focus on promoting audiences’ exposure to diverse information. The rationale for this goal has been that accurate beliefs and perceptions are necessary for good decision-making and for good governance in democratic society, and that development of these accurate beliefs requires some degree of exposure to information that challenges one’s existing beliefs and opinions. The Internet has brought more choice for what news and information individuals can access. Observers have warned that existing media policies are ill-suited for guaranteeing exposure to political diversity in the Internet age, as people are able to choose more freely from an ever-increasing variety of sources, many of which cater to and present a very narrow range of viewpoints. Given this range of choice, they argue, Americans will increasingly live in ideological echo chambers and polarization of different political groups will increase. Republicans and Democrats already read different newspapers and watch different TV news stations. They read different political books. They even live in different places. The sources to which they attend are echo chambers: left-leaning and right-leaning blogs rarely link to each other and comment threads contain little disagreement. If people prefer to avoid hearing challenging views, we may see even greater political fragmentation in information consumption as people get better tools for filtering the news based on their own reactions and reactions of other people like them.