It could, however, put some of the less-well-run dealerships out of business. The equilibrium number of dealerships might be smaller than it is now, as reduced margins support fewer salespeople. I'm not saying that's necessarily a bad thing overall, but I can see why the dealers might not be too keen on it.
Hardly, they have great marketing, but not exactly bare bones pricing. They cost the dealer 300$ for the sales lead which means their price is always higher than what a dealer will do directly. Last time I checked they where 600$ above what the dealer was willing to offer after a few minutes of haggling. Though, it's not a bad price if you hate haggling.
Hint, most dealerships make more money from their service departments than their sales floors. Use that to your advantage when buying a new car.
