For an up-and-comer in an intellectual field, insightful thoughts are a limited resource, and should be carefully allocated. Once can say interesting things in public, or one can devote the effort to more professionally productive writing. Or, one can save the effort to be insightful for professional writing, and write less insightful comments for the public. Which carries the risk of saying something that is dreadfully wrong, instead of merely a little bit boring.

It always astonishes me to see the volume of high-quality blog writing by academics in my field (i.e. law professor and lawyer blogs). I can barely write something interesting twice a month, and some folks write better stuff twice or more per week. If I really wrote that frequently, my writing would be an order of magnitude worse, with attendant risk of writing something foolish. I don't see my incentives justifying that kind of risk.