such blogs had tended to be not much more than cliques of common interest that reaffirmed partisan positions and denigrated alternative points of view.

While this is not universally true, surely everyone can think of a large number of political blogs where this IS true? For every Piping Shrike or Pollytics there are plenty of sites where smug, mindless groupthink in the comments dominates the culture.

As long as the crap remains publically prominent, it will be easy for people to maintain misconceptions like Mr Edwards’.