If you have comments, you encourage discussion, not a back-patting party. Often, we can learn more from dissent than from agreement.
For bloggers who have problems with that, well, they don't need to have comments. That's everyone's right. That's the trend I see among the pundit/political bloggers, especially on the right. Many don't risk having comments because they can't risk intelligent challenge. Their tenor is: "I'm right and you don't matter." Not a pretty picture that way either.
Personally, I think the default should be to have comments or risk becoming just another bully pulpit and a less powerful medium overall. . zzzzzzzzzzzzzzzzzzz. But that's just my opinon.
Jesus but we've become a self-important bunch in the last year. Sometimes we make me sick.