Legal scholar Cass Sunstein has described an undesirable phenomenon he calls "group polarization"—the Internet can accelerate the tendency of people to gravitate to groups that agree with their views, thereby making extremism more likely (from his Oct. 2000 Yale Law Journal):
The central empirical finding is that group discussion is likely to shift judgments toward a more extreme point in the direction indicated by the median of predeliberation judgments. This is true if a group decision is required; if individuals are polled anonymously afterwards, they are likely to shift in precisely the same way.
A new study by the Project for Excellence in Journalism shows that a similar polarization or "narrowing" is happening in news coverage as well.
As AP writer David Bauder puts it, "The Internet has profoundly changed journalism, but not necessarily in ways that were predicted even a few years ago."
The most worrisome statistic might be this (from Bauder's article):
Two stories — the war in Iraq and the 2008 presidential election campaign — represented more than a quarter of the stories in newspapers, on television and online last year, the project found.
Take away Iraq, Iran and Pakistan, and news from all of the other countries in the world combined filled up less than 6 percent of the American news hole, the project said.