I agree with ejaymd11; they need to subsidize the phone on all carriers. You can't really do things like introduce all world phones (ala the iPhone 4s) or try to sell phones unlocked if you aren't operating from a position of strength, and up till now the Nexus brand has made no serious inroads with consumers.
The Samsung teaser ad looked like a smart and consumer-oriented commercial, and the fact that Verizon wants this as an early exclusive both argue that Google and Samsung are going to being making a concerted push to get the Nexus brand into the mainstream. And that would be the best possible thing for Android going forward.