The Web offers more content sources than ever before, from people with storied, credentialed histories, as well as anonymous bloggers and commenters who may present themselves as experts, whether they have knowledge of their space, or not. With so many comments and posts being written in a constant deluge of words, how do readers determine where they'll stay? How does one gain credibility in this new medium?
Some would argue that only through proving their posts factually accurate, or their opinions applicable, can bloggers draw credibility and respect, leading to repeat visits and consistency. The argument is that through increased awareness of opposing viewpoints, visitors can learn from the other side and adopt new insight. But I think often the opposite is true, and the Web makes it even easier to "stick to your guns". It is human nature to seek out a community of peers and equals, of those who yearn for the same things or have parallel experiences. At the same time, there are also those who have opposing viewpoints, undesired by the first group. As such, two polarized and wholly separate communities will grow and thrive. And after visitors find themselves acclimated to a community, they aren't likely to visit its polar opposite, but instead will latch onto branches of the same tree and stick close to the familiar and comfortable.
The most clear example of this on the Web is in the political realm. For left-leaning political discussion, Daily Kos has no equal. On the right, you have the Free Republic. The two sides are in such contrast that no one sane user would be registered and active on both sites. A Daily Kos user would instead migrate to friendly sites like Talking Points Memo, MyDD, Eschaton and This Modern World, bookmarking each, and slowly traversing the left-o-sphere, rather than getting a more broad view. Similarly in technology, you see a bifurcation of opinions - Macintosh vs. Windows, Open Source vs. Microsoft.... basically, Microsoft vs. anybody. For Mac fans, one would move from MacNN and MacInTouch to MacCentral to Apple message boards, to the rumors sites aplenty... MacRumors, Think Secret, AppleInsider. But there's no interest from a Mac user to join the WinSuperSite or worship at the throne of John Dvorak.
To measure credibility on the Web, visitors are looking for people who already agree with their opinions. They're not so much looking to be changed or to gain information from other viewpoints, but to instead become more hardened in their positions - just as you would in the real world, with Fox News viewers kissing up to Rush Limbaugh. There may be more sources for news out there, more viewpoints, but visitors aren't interested. They just want to hear that they are right and there are others there to cheer on their pre-conceived notions.