There have been many valid complaints concerning the networks drastically reducing the amount of hours devoted to the infomercials/conventions, but at least two networks are providing access to the entire event on digital cable and more importantly, streaming video on the internet.
yahoo article on network coverage
It seems to me the more people that watch on the internet, the better. I only regularly go to msnbc.com, but the depth of coverage on any given issue exceeds any of the one-dimensional Tom Brokaw broadcasts. The power of interactivity to fact-check the politician's speeches as they speak, or even just the accessibility of watching on and off while you work at the computer makes it really valuable.
The more the public has to go the web for these large events, the more they're directed to get their news from the web, and eventually America is better informed? If I were head of a network news division, I'd be nervous about the possibility of lower ratings, not to mention the loss of control of what the public thinks and who they'll vote for.