Here's the thing...
DRM, DPP, whatever, are attempts to technically impose the physical world onto the digital world. The physical world naturally has the notions of exclusivity of ownership and scarcity, whereas the digital world doesn't.
Trying to graft a simulation of the physical world onto the digital is cute, but won't be successful. Because of the nature of the media, it will be bypassed by those who wish to do so. The morality and desire to apply the economics of scarcity to digital media simply don't matter with regards to whether someone will or won't copy the information.
In short, it's a waste of money. Attempting to find ways to use the nature of digital media to make money would probably result in a better return on investment.