Digby says what needs to be said, but let me add a few things.
The current model of politics is unlikely to be overturned anytime soon. The netroots may complement it and may supplement it, but they're unlikely to replace it. Unions can do what is necessary - put bodies in position at key moments. When a candidate is running for local or statewide office, it's absolutely vital to get bodies at events. Bodies equal audiences, audiences equal press coverage.
That certainly isn't the only role unions play, but it's one which is hard to duplicate.
