[F]rom the standpoint of democracy, filtering is a mixed blessing. An understanding of the mix will permit us to obtain a better sense of what makes for a well-functioning system of free expression. In a heterogeneous society, such a system requires something other than free, or publicly unrestricted, individual choices. On the contrary, it imposes two distinctive requirements. First, people should be exposed to materials that they would not have chosen in advance. Unanticipated encounters, involving topics and points of view that people have not sought out and perhaps find irritating, are central to democracy and even to freedom itself. Second, many or most citizens should have a range of common experiences. Without shared experiences, a heterogeneous society will have a more difficult time addressing social problems and understanding one another. [Emphasis in the original.]
James Miller disputes Sunstein's assertion, though, in an excellent essay in Tech Central Station titled "The Depolarizing Power of the Blogosphere". "Although the Blogosphere can polarize," Miller writes, "I believe that on net it will reduce political differences among Americans." He elaborates:
Americans are ideologically divided but also connected across multiple dimensions. The Internet does allow individuals to find niche blogs which cater to their particular viewpoints. But the web also has blogs which bypass traditional ideological divides. For example, although the mainstream media views politics through a Republican / Democratic lens, some of the most popular blogs take a libertarian viewpoint that, depending on the issue, could favor either party. I suspect that many Americans who had considered themselves Democratic-hating Republicans found, after visiting blogs such as Asymmetrical Information, that they really are somewhat libertarian and in fact on a few issues had more in common with the Democratic left than the Christian right. [Emphasis in the original.]
He ends by proposing what may well come to be called "The Instapundit Test". He writes: "The links on Instapundit.com represent the most popular filter used in the Blogosphere. If you click regularly on Instapundit's links then a good test of how filters affect polarization is whether Instapundit causes you to read more or less diverse material."
I'm an Instapundit junkie, and there is no question that the most popular blog on the internet has certainly increased, by far, the diversity of my reading. QED.