When considering bias in the media, one must look for the odd media outlet that is decried by both sides for its bias. This regularly occurs in reference to the Public Broadcasting Service, or PBS. PBS' focus has never been on making money, or keeping shareholders happy. Their only goal is to inform the public.
The BBC is widely regarded as independent and unbiased because its charter demands that it gives equal air time to politicians from right and left. Furthermore, its presenters are not allowed to voice their own political opinions on air. However, because the rest of the media is privately-owned (much of it by that frothing right-wing nutjob, Rupert Murdoch), the BBC’s political coverage is seen by right-wingers as having “a left-wing bias” because it gives equal wight to the views of left- and right-wing politicians.
Sadly, independent journalism is a thing of the past. Too much money in the advertising coffers from special interest groups drives the opinion of network news agencies, while newspapers are slaves to any dollars and avoid controversy to keep the money. As a 20 year veteran of the newspaper industry I see more and more editors and publishers bowing down to advertisers instead of original thought and real journalism. They feel this is the only way to keep the product alive.
As far as mainstream media, the system has become more interested in making money and selling issues or gaining viewers for their shows than reporting events in an unbiased manner. However, with the widespread use of the Internet, independent journalism has started to re-emerge. It is easy for anyone to start a blog, and some of the new writers out there are beginning to unearth important information that the mainstream media ignores. One such journalist was Julian Assange, and his attempt to educate the world caused a massive uproar.
To accomplish these things the media tailors their scope and their mission in order to get stories, viewers, air time, buzz, you name it. They answer to their parent corporations and they want ratings, they do not care if the stories are biased or not. In fact the parent corporations are sometimes the one who make the news outlet biased.