The paper only goes into the IP implications, but I think those are relatively minor compared to most implications of low-cost 3D printing. 3D prototyping make

The paper only goes into the IP implications, but I think those are relatively minor compared to most implications of low-cost 3D printing. 3D prototyping makes it a lot easier for people to build and improve weapons. You could, for example, print your own AR-15 lower receiver and buy the rest of the parts. Or print your own full-auto sear. Or print your own sound suppressor (silencer). Today, building those things requires specialized knowledge and expensive tools. That will change as 3D printing goes down in price and up in quality. The advantages of this technology outweigh the downsides, but it's good to be aware of the downsides.