Kanye West is afraid that 3D printing will kill the shoe industry. Why is Kanye afraid? Maybe because adidas, who makes his Yeezy Boost 350 (which you can get on the second-hand market for a cool $1,000), said it's making a running show with 3D-printed materials. Now enterprising bootleggers might start printing their own Yeezys.
Kanye might be right to worry -- the laws against 3D printing are pretty lax. But there are a few things that are illegal to 3D print.