"We, the most powerful democracy in the world, have developed a strong norm against talking about politics. It's fine to talk about politics with people you agree with. But it is rude to argue about politics with people you disagree with. Political discourse becomes isolated, and isolated discourse becomes more extreme. We say what our friends want to hear, and hear very little beyond what our friends say."-- Lawrence Lessig, Free Culture: How Big Media Uses Technology and the Law to Lock Down Culture and Control Creativity", 2004, The Penguin Press. (Free PDF and ebook versions available.)
[Lessig goes on to discuss role of blogs in addressing this problem, saying among other things, "Yet even if the number of readers is small, the reading is having an effect."]