Saw this on Hackaday and had to share it. This guy has figured out how to embed a small copper wire in his extruded plastic from his 3d printer. It's very basic at this point as there's no way to have the machine cut the wire, or to hook it up to anything. This could be the beginning of the ability to 3d print circuits. Some example applications he lists for this include:
3D printing as a whole is still a very young hobby. You could compare it to ham radio at the very beginning with the spark gap transmitters and no regulating body. Or even hobbyist computing in the 70s when you had to build your own computer if you wanted one. The machines are slow and require a lot of fiddling to get a good print. But there's lots of experimentation, not much is set in stone yet and there's a lot of discoveries to be made.