For the greater good?
In an ideal world - sure. In reality - not a chance
In all honesty, I don't think it's going to be a huge issue. It's not like media, where it's easy and practically free to make your own copy. With physical objects there's cost, effort and other factors involved. Take for example a car part:
*Cost of materials
*Cost of printer
*Space for printer
*Time and effort to set up printer, feed in materials, etc.
*Guarantee provided by manufacturer.
While yes - even following all that you might save money, I don't see more than a handful of people finding it worth the effort, and given the cost of the printer, you'd likely have to produce quite a few parts before actually breaking even. For most people the possibly 10-20% saving (would it really be more than that?) just wouldn't be worth the time and effort.
After all, anyone with a garden could grow their own veg at a much lower cost than supermarket, and yet the majority of people don't bother.
3D printing should not go into homes, it could and will be a risk to the public if people starting building their own fire arms. People will. Nothing will stop them.
This is already a possibility. Length of pipe of the right diameter, a couple of springs in the right places and a nail and you have a rudimentary shotgun (thanks mispent childhood!). Getting the ammo is the difficult part in this country, so this won't really have much of an effect.