Julian Sanchez, one of Megan McArdle's guest bloggers, has a very interesting post
highlighting Jay Rosen's post on media bias
The debate on media bias is generally rather partisan. Critics on the left believe that the media is pro-business because they are businesses, and that they do no want to risk angering those who buy advertising from them.
The right sees that most journalists are college educated cosmopolitans (who mostly ignored economic incentives when it came time to choose a career) who mostly vote for democratic candidates, and labels the journalists and therefore media as leftists.
Jay Rosen highlights a lot of the more complicated biases that he thinks matters more than the above arguments. Journalists gain status by publishing stories that anger one or both sides of the political spectrum (He quotes some journalists who are proud of getting attacked by both the left and the right in the same week). They gain more status from a take down than from a glowing profile, so they are apt to report on more pessimistic events. Skepticism is valued, and journalists who are true believers aren't taken seriously. Journalists need to produce stories that are seen as bias free, so instead of trying to figure out the truth they take quotes from both sides and try to appear like they are in the center. Journalists identify some ideas as outside the mainstream and ignore them completely (placing the ideas in a "sphere of deviance"), or if they do mention them they make sure to present the ideas as extreme or impossible.
Many more of these biases are listed, and they are quite an interesting framework for seeing how news stories are biased to present certain types of views.
However, the existence of these biases don't rule out additional biases. For the average person, it is very difficult to identify with arguments of the opposing side. Journalists trying to be neutral in a "he said/she said" story know which leftists arguments work, but may be less likely to pick the best rightist arguments. If true believers aren't taken seriously, then both hardcore environmentalists/communists and the religious right will be excluded from the conversation. This is still biased though, because this excludes a larger percentage of the right than the left. Also, the placement of the "sphere of deviance" might be more centered around their views, which could lead to views of the slightly far right being taken less seriously than views of the slightly far left.
One additional critique of Jay Rosen's post is that he assumes that reporters are big believers in the law of unintended consequences while it seems like this generally isn't the case. The way stories are structured many potential unintended consequences of government action are often ignored or merely given a single sentence towards the general idea of unintended consequences towards the end of the article. The framework of "There is a problem, here is how they are trying to fix it" dominates the story. Of course, my generally libertarian perspective is in the sphere of deviance, so perhaps Rosen's post does account for this issue.
A person's perspective on media bias depends on their own position on the spectrum. Someone on the far left would see the media as failing at its job as a corporate watchdog, and might attribute this to corporate influence. Those in the center left to center might see no particular problem, while those farther to the right see a bit more bias as their views are relegated to the "sphere of deviance".
With the advent of the internet, some parts of media might become marginally less biased - they are more likely to be called out more often when they show any significant bias. The bigger effect is that there are more openly biased websites, giving viewpoints from a particular ideological perspective. People can choose to take their news with a known bias, especially if it corresponds to their own bias (in which case it doesn't seem as much like bias as a correct viewpoint to the reader), over a vague bias. This is happening on the left and the right. The Huffington Post is a popular openly progressive news portal and there are many slightly less popular (when measured in hits) conservative news websites and blog networks. As more people switch their news consumption to openly biased sources, the idea of a general media bias may become less important going forward.