Who comments on blogs?

The Freakonomics blog just asked posed an interesting question.  The question is "Who comments on blogs, and why?"

They point out that there is always a much larger number of commentors than there is posters.  What drives those posters to take the extra time and effort (actual amount of effort varies from blog to blog, but it is always more than 0) to post rather than just reading and moving on?  My initial thoughts are entered in their comments section under the user name Sloar.

The more library specific question that the post brings up for me, is what are libraries trying to gain form our blogs?  This is probably a question all library blogs should consider as we develop our blog presence.  Are we looking for merely an electronic bulletin board where we can post notices online or are we trying to facilitate a place for discussion?  A discussion blog should make posting as simple as possible and should allow anonymous posting, or at least in my mind it should.  A bulletin board blog doesn't require such easy access, although it may not do any harm.

In any case, it might be worth following the Freakonomics discussion if you're interested in seeing why people do or don't bother commenting.