Felix Salmon notes that econobloggers are better publicists than reviewers:

even as papers get a lot of play in the blogosphere, economists are generally still reluctant to make substantive criticisms on public blogs rather than in private seminars. (This doesn’t apply to policy debates, of course: they’re a different kettle of fish entirely.) The result is that economic papers get much more pre-publication attention than ever before, with most of it being very uncritical. By the time the paper’s gone through peer review, public attention has moved elsewhere.

Of course, every author loves his/her publicist, while critics are rarely thanked. And unless the criticism is particularly entertaining (such as Dan Davies’ four-part Freakonomics take-down), it is unlikely to be widely read. So the incentives are clear.