Reading the news online today, I was reminded of what Halberstam calls "The Afghanistan Principle:" journalists have more freedom the further away their subject is. If you're writing for the New York Times, you can say pretty much anything you want about the President of Afghanistan, but if you're too critical of the Mayor of New York, your editor will probably hear about it.
Good editors and good publishers do their best to fend off outside pressures, but they're only human. If fellow CEOs are haranguing the publisher and pulling ads, he's not going to be happy. The more unhappy he is, the more pressure editors and reporters will feel. At the other extreme, some publishers quite openly insist on content that conforms to their views.
As a reader, the best way to get better journalism is to reward those who supply it. Write nice letters, patronize advertisers, and tell the advertiser where you saw the ad. Positive letters are especially powerful, since so many people write only when they have complaints.
As a citizen, the best way to stay informed is to remember that the Afghanistan Principle works in reverse, too. There's lots of excellent coverage being written outside the US. Even government-controlled media at least illustrate what that nation's leaders want their people to think.
Needless to say, the Internet is the best anti-bias tool ever created. If you aren't reading at least one foreign news site regularly, you're seriously missing out. Be aware, though, that the Afghanistan Principle applies to blogs, too: like most bloggers, I would think long and hard before picking a fight with a neighbor or a client. The best approach is to use a variety of sources and make your own decision.