The University of Nottingham's Phil Moriarty has written an excellent piece in Times Higher Education looking at post-publication peer review, whether through official channels or via blogs.
Responding last year to criticism of their field in the wake of the serial fraud committed by Diederik Stapel, three social psychologists - Wolfgang Stroebe, Tom Postmes and Russell Spears - published a paper in Perspectives on Psychological Science, titled “Scientific Misconduct and the Myth of Self-Correction in Science”. This provided compelling evidence that, across the disciplines, peer review fails to root out fraud. This is worrisome enough. Yet even basic errors in the literature can now be extremely difficult to correct on any reasonable timescale.
Meanwhile, Jonathan Jones points us to this post - at once appalling and hilarious - about just how difficult publishing comments has become.