Are blogging professors wasting their time?

Here's a very uplifting article about the benefit of blogging to professors. Is it just a waste of time, or is there a benefit to the professor, the university, society?

Blogs considerably raise the profile of University professors, which is good for the University. Through their archive of posts, professors advertise their expertise in a given field. Establishing that authority leads calls from the media — and the University's name appearing in print.

Still, I would argue there's still something to be said for the view that it's a timesink.