Tyler Cowen writes,

Chess players who train with computers are much stronger for it. 
They test their intuitions and receive rapid feedback as to what works,
simply by running their program.  People who learn economics through
the blogosphere also receive feedback, especially if they sample
dialogue across a number of blogs of differing perspectives.  The
feedback comes from which arguments other people found convincing.  Do
the points you wanted to hold firm on, or cede, correspond to the
evolution of the dialogue?  This feedback is not as accurate as Rybka
but it's an ongoing test of your fluid intelligence and your ability to
revise your opinion. 

Not many outsiders understand what a powerful learning mechanism the blogosphere has set in place.

Ezra Klein tweets, "The blogosphere is like a graduate seminar that never ends."

Commenters and other bloggers keep me on my toes. If I through out a quick, stupid thought, odds are that someone will tell me that I'm a moron and then explain why. This is a very good thing.

Also, I'm constantly reading other bloggers and articles in the paper looking for blog fodder. Much more than I did pre-blog. I'm writing every day, way more than I did pre-blog. I'm forcing myself to take sides on controversial issues and justifying my decisions.

It does take me away from work on longer, more polished prose. But when I carve out the time to finish my projects, I sure have a lot to say.