First, there is the contempt for 'amateur' writers, endemic in professional journalism. Hacks are always astonished by anyone who writes for no pay, so upwards of half a million such amateurs now publishing blogs leaves the pros speechless. It also leads them to deride blogs as an epidemic of vanity publishing rather than the glorious outbreak of free expression it actually represents.
Second is the assumption that anything written by an amateur is, by definition, worthless. Yet journalism has always been, as Northcliffe observed, 'the art of explaining to others that which one does not oneself understand'.
In fact, when it comes to many topics in which I have a professional interest, I would sooner pay attention to particular blogs than to anything published in Big Media - including the venerable New York Times. This is not necessarily because journalists are idiots; it's just that serious subjects are complicated and hacks have neither the training nor the time to reach a sophisticated understanding of them - which is why much journalistic coverage is inevitably superficial and often misleading, and why so many blogs are thoughtful and accurate by comparison.
Third, there is the problem - not often touched upon in the New York Times, by the way - that many controversial public issues are ignored by Big Media for the simple reason that the ideological and commercial interests of their proprietors preclude it.
I'm amused that the journalistic community, so committed to globalisation and market forces, is terrified of having to compete in a market of ideas.