Publishing rarely lucrative

In the Shirky piece I referred to earlier, he writes “Right now, the people who have profited most from weblogs are the people who’ve written books about weblogging.”
I’m not aware of the sales figures for any of the handful of books out now about weblogging, but I sort of doubt that these authors have profited most, based on what I know about book deals, advances, royalties, and so on.
I suspect the people who’ve benefitted most financially from weblogging so far are people who already had professional writing careers but who have gained more attention or “bookings” from the self-promotional benefits of doing the blog.