Commenting on papers

Last month Nodalpoint highlighted the fact that BioMedCentral have collected all of the recent user submitted comments about the papers that they publish on a handy-dandy comments page (there's also a "latest comments" box on the BioMedCentral front page). Some of the Nature journals are also inviting commentary on papers via their blogs (like Free Association).

Now Complex Medium has pointed out that Cell are accepting user submitted comments on one or two highlighted papers per issue.

I'm interested in seeing how these experiments turn out - in particular, what sort of comments will people leave, and how often? The downside to allowing online commentary, I suppose, is that some sort of human moderation is required to keep out spam and kooks. The upside is that it's easy for people to provide useful information like this (and this, which is possibly unfortunate for the authors).