Most rigorous studies conclude that there is no consistent partisan or ideological bias in the mainstream American news media. This suggests a natural but little-asked question: Why isn't there more bias in the media? A year spent working as a journalist suggests a possible answer: Advancing a political perspective does not help secure a place on the front page. Instead, the core incentive for a journalist is to be interesting. Interesting work that reveals the essence of a situation garners a more prominent spot in the newspaper and all its associated benefits. Because “interesting” sources are found on both the left and the right, among Republicans and Democrats, balance does not require a Solomonic commitment to fairness. Rather, balance can be achieved merely as a by-product of the effort to be interesting.
That is the abstract of the paper "An Interesting Bias: Lessons from an Academic's Year as a Reporter" by David Nivena (Political Science & Politics April, 2012). Alas, I did not find the paper online.
Is the author referring to some kind of median-audience theorem? A lot might depend on the audience. May be some audiences don't like to listen to "interesting" arguments, but arguments that confirm prior believes. In other words, what is interesting might be very subjective and depends on the world view of the audience.
Interesting bias in blogs?