Reviewer's ethics

Brit classicist Mary Beard has advice on reviewing, based on her review of Robert Hughes's book Rome, which was nominated for a "Hatchet" award in Britain (There's a Hatchet Award? Can we have one?):

I have never met Hughes, but if I were to have the pleasure, I would say just what I wrote to his face. And that has always been the ethical touchstone of a review. If you couldn't say it to the author, then it's a skewering, so don't.

The review is here, if you want to test principle against practice.