You know something? Steemit seems to be really good at burning out people pushing high volume, low quality content. Seriously. Even a crappy post takes a few minutes to put together, and there are very few people that can keep churning that crap hour after hour without any kind of reward. Seeing $0 on every post is a constant reminder that you should be spending your time elsewhere.
I agree there's going to be a flush of spam as people chase pennies trying to make millions, but the whole system seems very well designed to discourage that sort of thing. I'm sure someone is going to game the system in a way the devs never thought of, but so far, it seems like Steemit is making people dig deep and push out as much quality as they can muster.