There are many useful applications of RPV's and the general public should be allowed to enjoy those. However that same general public also has the right to be protected from unreasonable danger. Drones *do* fall out of the sky and therefore can harm people and property.
So instead of trying to register everything I'd say there should be ate least two categories of drones. One 'free for all' that is sufficiently lightweight and slow so as not to cause any serious harm and another which is everything else. You should not be able to buy the 'everything else' category without at least some training.