3.1 - What if it was governmental rather than corporate, and laws were put on the books to restrict what was allowed to be printed. Unenforceable?
3.3 - Perhaps you underestimate the power of lawyers? They are quite willing to try to prevent people from doing something that you might consider 'outside the bounds of normal capability'. I guess AB is really talking about the unenforceable nature of IP on objects which CAN be printed. What about that?
2.1 - Feasible and simple are certainly in different ballparks. I think there are more possibilities to replace the motors and make the electronics using the printers than you might realize.
2.2 - Replace with cheaper alternatives, or replace in the first place? Some little plastic widgets are hard to make
2.3 - I feel like you're saying that it will be both an evolving community AND nothing special, so i'm confused. I point out that no one thought that computers would be in homes until people started to tinker with them in their garages. Are you sure it's not the next big peripheral?