Dan Gillmor's Guardian column, "Andrew Breitbart and the unwilling suspension of disbelief," explains his theory of online credibility and talks about how to be appropriately skeptical of different sources. Gillmor is dubious about anonymous comments, though he's careful to defend the value of anonymous speech.
Breitbart will never rate as low as some people on my BS scale, because he stands behind his own words. I respect him for that much, unlike the anonymous commenters who hide in the virtual bushes to snipe at others. Anonymous sources in journalists' stories are generally contemptible for the same reason, especially when their role is to attack. Our disdain should extend in those cases to the journalists who grant this favour; they are doing their own reputations no good at all.
This is not an attack on anonymity, incidentally. We need to preserve people's ability to speak without being personally identified in many cases. Without anonymity, for example, many whistleblowers will not expose the crimes of governments and large enterprises – just one reason to preserve it. I will discuss this more fully here soon. But my bias in discourse is that we should stand behind our own words, and that we should encourage others to do the same.
Credibility is a hard-won asset, and all too easy to forfeit. Breitbart's credibility has improved in the wake of the Weiner affair. Will it move into positive territory? I will not hold my breath, but I will hope so.