The issue of confirmation bias has come up repeatedly here before. Basically, people evaluate new information in a way that is far from impartial; new information that seems to confirm pre-existing beliefs is generally filed as evidence for the appropriateness of those beliefs, while contradictory information is downplayed or ignored. While this phenomenon is ancient, there does seem to be good reason to think that it may be especially acute now, as the media becomes more personalized and segmented.
That danger is highlighted by Harvard academic Ethan Zuckerman, who gave a TED talk on how social networks mislead us. Because we are exposed to the thoughts of people who are already much like us, we are at risk of being convinced that we are more typically than we really are, and our views are more mainstream and justified than may actually be the case.
How much of a problem would people say this is, both from the perspective of being well-informed citizens and in the context of being effective in promoting particular policies? Is there any way either social networks or individuals can combat this entrenching of confirmation bias? For my own sake, I have been trying to incorporate more articles from newspapers I disagree with into my daily reading.