My personal opinions have been mentioned by others.
1) It's an answer to a question nobody asked.
2) It's a novelty.
The biggest problem I see with it is that you are 100% responsible for EVERYTHING that leaves your gun. Every 410 pellet that comes out of that thing (the wad too) has your name, address, and a few million lawyers attached to it.
If you shoot a 10" pattern half way across the bad guy's head, where is the other half of the scattering shot going to end up? It may not be lethal but there are still consequences of any projectile you launch.