The problem I see all too often in the blogosphere, and in fact, to an increasing degree in society at large, is that people are becoming less likely to read and listen to opinions that challenge their own. This is a grave mistake. By listening only to opinions that mirror or closely parallel your own, there can be no intellectual growth. It takes the challenge of opposing opinions and the act of debating opposing opinions in a civil and intelligent manner to not only cull bad ideas, but to refine good opinions. If you look to the left sidebar on this site, you'll find that most of the blogs to which I link, I disagree with to a greater or lesser extent. Even the ones with which I agree run contrary to some conventional wisdom.
There are other, slightly less obvious, dangers to listening only to those with whom you agree. Without listening and truly debating, it becomes easier to demonize those who disagree with you. By debate, I don't mean this "Crossfire" crap. I mean an honest discussion of issues, cordially but firmly expressing your disagreement, and explaining why you hold a particular stance. I would go so far as to say that listening only to opinions with which you agree is nothing short of intellectual incest, and as with the royals in medieval Europe, incest is a very detrimental thing. As a result, whenever I see this occurring, I challenge it, and I'm not always nice about it. Though I regret the fact that I sometimes channel my inner jackass, I do not and will not apologize for the end result. If I have caused someone to think and challenge their own ideas, I consider it a good thing. So I encourage everyone to find blogs with which they disagree, engage the hosts thereof in friendly debate, and further hone your own views, and allow yourself to be swayed. Think for yourself, but keep an open mind. Remember that no one is perfect, and no one is correct all of the time. I certainly know that I'm not. But when looking for opposing opinions, expect the same standards of quality you should demand of any other source of opinions. It's hard to hone your opinions by only challenging weak opinions, in much the same way that people don't become physically stronger unless they push themselves beyond their current physical limits.