If anyone can exert pressure on book publishers to ditch DRM, it's Amazon, but why would they? Aside from The Greater Good they've got themselves a nice little vendor lock in, and unlike Apple who was making money hand over fist with the iPod and using the iTunes store to help get consumers to start building digital libraries, Amazon isn't making staggering amounts of money on the Kindle and they really need people to stick on the platform.
Seems like a few publishers have seen sense regarding DRM (Tor and Angry Robot are the first two who spring to mind), so maybe they'll eventually wise up and start dropping the DRM requirement.