The New York Times has a good essay by Richard Posner on the effects of choice on the traditional media and journalism. He looks specifically at blogging and its self-correcting nature.
He echoes many of my concerns about the echo effect. It is a myth that people read the news to become better informed. The audience dictates the news more than people realize. No audience, no advertisers, no station or newspaper, as Posner documents. (Even a political publication needs financial support from someone.)
Blogs do not face the same need for a larger audience.