It is almost impossible for any network or journalistic publication not to be accused of some media bias. Subtle things like word choice, time limits on programming, needs to have sponsors in order to run a business, and choice of sponsors may all be examples of media bias. (wiseGEEK)

Research into studies of media bias in the United States shows that Liberal experimenters tend to get results that say the media has a conservative bias, while conservatives experimenters tend to get results that say the media has a liberal bias, and those who do not identify themselves as either liberal or conservative get results indicating little bias, or mixed bias. (Wikipedia)

Nothing ratchets up the perennial debate over media bias like a presidential election. But as Tim Groeling, a political scientist at the University of California, Los Angeles, observes, public discussions about media bias are often just “food fights,” with pundits and partisans throwing around anecdotes. (Scientific American)