[philipkglass]

It seems like it could lead to a world of abundance for everyone. One potentially severe complication: if machines can make anything there's a blueprint for, they can also make all manner of weapons. What if the occasional unpredictable spree killer could fab up a crude cruise missile full of nerve gas instead of buying a bunch of rifles? Or even what if someone fabs a throng of standard tree-trimming robots and reprograms them to trim the limbs off humans instead?

Most people aren't willing to kill other people. In a world of abundance, I expect that even fewer will be willing. But the few killers who remain could have vastly amplified powers of destruction. I don't like how Marshall Brain's Manna solved the violence problem, but I haven't got any great answers of my own.