Because they are so busy, referees often do a lousy job of reviewing
submitted papers, and they often get away with it because they act
under the cover of anonymity. With authors blogging their reviews,
however, reviewers might feel pressured to be more diligent in their work.
Although they remain anonymous when authors blog their reviews, many in
their smallish research subcommunities are surely able to recognize who
wrote a particular report. And even if they aren't, mediocre reviews reflect poorly on the journal or conference.
Now here's a potential fly in the ointment: given the number of
articles that are submitted every year, if everyone took the time
needed to write good referee reports, would there be any time left to
do actual research?