Here are a couple of examples, the Competitive Enterprise Institute's blog, the “Open” Market and the Cato Institute's Cato-at-Liberty.
This is “blog spin” pure and simple. By not allowing comments on your site, there is no sharing of ideas or disagreement, which is one of the best features, if not the most most important and beneficial aspects, of blog technology.
So Cato and CEI, get down from your preaching pulpit and open up your blogs to your fans and, of course, your detractors. What are you afraid of?