If I can add my two cents worth to this very interesting discussion...
The burden should be on the individual, as Nick states so well, until it is proposed to be used for transporting the public or their cargo, or operating it where it can endanger folks on the ground. The FAA system seems to work quite well in this regard- I can point to Burt Rutan's Voyageur program where he thanked the President for only requiring one piece of government paper for him to fly the aircraft. More recently, the Groen Brothers gyrocopter seems to have progressed quite well without a mountain of paperwork or requirements to get it to the point where it is nearly ready to be looked at in detail for certification.
So, the system works reasonably well in the USA as far as getting something new or unusual developed. The problem then becomes getting it certified. But that's another story.
Shawn