One of things that I often edit at my newspaper is the "Feedback" section. We receive comments from readers in the form of phone calls, letters and e-mail. Either our Editor (who oversees everything) or out Managing Editor (who just oversees reporters and the like) responds to them. One of the things that I've noticed that oftens comes up is how biased journalists are. The simple truth is that no one can be unbiased (without opinion). It is just the way it works. Because of this, no news article can be unbiased because people are asked for their opinions in interviews; their answers make the story.
What a journalist strives to do is show as many opinions of a single subject as he/she can, being careful not to give any one side too much weight. The ways stories often become biased is if a source doesn't want to speak to reporters. Also, people tend to see what they want to see. Everything we do or believe in life is shaped by an opinion. In the same way, when we read a story that talks about something that we believe in, we will either be happy because it agrees with us, or pissed off because it lets the 'wrong' people have their opinion too.
Finally, what few people realize (and some journalists don't realize) is that journalists must sacrifice something that most hold dear to remain 'unbiased' to their readers. This, of course, is thier own opinion.
When I took a job at my paper, it was implicit that I can't allow my opinions to create biased work, or even to create the illusion of a bias. This means I can have nothing to do with politics, unless I am reporting on it or privately voting. It also means I cannot outwardly express my opinion. I cannot have bumber stickers that show strong support for a specific view, especially because I have my parking permit (which has my paper's name on it) displayed at all times. I also have to be careful if I volunteer for something. I currently work with the SPCA. I have done so since I was in college because, first I missed my family pets and secondly because the SPCA needed help. But if my post with the SPCA were to ever cause my work to become biased, or be perceived as biased by a reader, I could conceivably get fired. That's it. The readers expectation that the news remain unbiased at all times requires this sacrifice of reporters and editors (disregarding the Editors who are charged with writing editorials; ironically enough, editorials are the real origin of the news in this country).
I have a politically-active friend who, upon hearing this, said she would never work for people who would require such a thing. I responded by saying that it is a necessary sacrifice to make sure people, including her, can be informed citizens and have a right to be politically active.
So my whole point is this: Before you say a paper (or the news) has become biased, first ask yourself if it is you who are really holding that bias and don't want to admit such a thing. Because I know damn well that every reporter/editor I know works harder to remain unbiased than most people do at being 'good' at their own jobs.