"site visitation self selection" There is an increasingly polarized nature to policy and political debate today.  [For a classic example, Bill O'Reilly, of "The O'Reilly Factor," accuses leftist Air America radio of being disgusting and despicable, and labels those who accuse (and document, correctly or incorrectly) him of distortions and hypocrisies, as "vile despicable human beings." More on this organization's points about O'Reilly's shows, which, left wing or not, we find reasonably credible (although some of the views expressed we do not agree with) more.]  On the Internet, this polarization gets exaggerated, as surfers can choose the sites that appeal to them, which, more often than not, will be sites that express a particular point of view.