It tends to be the legal system. With phycical books there was no question of going after illegal copies, but now with DRM you can actually go after physical co

It tends to be the legal system. With phycical books there was no question of going after illegal copies, but now with DRM you can actually go after physical copies, so the court demands that. Amazon "usually" doesn't have a choice in this matter. Of course the better way to proceed is to make sure they don't have a choice.