For the uninitiated, 3D printing is very much what it sounds like: devices which "print" three-dimensional objects by laying down layer after layer of material until the object is completely constructed. 3D printers are already being used to build custom-made lamps, artwork and prosthetics, among other things. 3D printers can even make most of the parts to make other 3D printers.
The really fascinating thing about 3D printers is that right now, the technology is new and fresh, and early adopters are only beginning to scratch the surface of what's possible to do with them (much as how when the internet was relatively new, people mostly only used it for direct communication, and all of the other aspects that the net has taken on were barely imagined). The problematic thing about 3D printers, though, is that they may essentially require that we rethink many aspects of intellectual property law.
Copyright protects many works that are long and complex, and can take the form of a variety of expressions. As a result, it was relatively unlikely that two people would create the exact same work without the second copying the first. In contrast, many people working on a practical problem at the same time may create similar solutions. For patents to be worthwhile, they had to cover all identical devices, no matter how they were developed. It was assumed that parties vying for a patent were sophisticated and would do a patent search before trying to solve a problem. Everyone playing the game understood that it was a race to file, and took necessary precautions.Traditionally, copyright law's intersection with the design of physical objects has been problematic. The Copyright Act stipulates that a "utilitarian function" of an item cannot be copyrighted: the idea of armrests on a chair, for example. However, a unique utilitarian work - for example, a one-of-a-kind chair with special swooping armrests that look like diving birds - can attract copyright in its uniqueness as being both a utilitarian item and also a work of art.
3D printing could change that. By democratizing the precision creation of physical objects, 3D printing may make the creation of physical objects nearly as widespread as the creation of copyright-protectable works.
3D printing makes all of this much more problematic because until now the reason unique utilitarian works have remained so is that they largely had to be completely hand-made, which encourages uniqueness. But if you can make your unique chair (or lamp, or what have you) and then scan it with a 3D scanner and just print out copies of it? At that point, you're mass-producing the item, and thus losing your copyright in it, because once an item becomes mass-produced its aesthetic features are deemed to change from being artistic in nature to being industrial, which does not attract the protection of copyright.
Similarly troublesome is that copyright protects that original chair because copyright is predicated on complexity of the creative process. As Weinberg pointed out, it's not very likely that two chairmakers will make the same diving-birds-armrest chair, because there aren't a lot of chairmakers in the world who would take the time to craft wood and springs and cushions in such a way. But think forward ten years down the road, when you can purchase a $200 3D printer and a copy of 3D Chairmaker 2020, software which will help you design a chair on your computer, giving you guidelines to make sure that your chair can support weight properly and be comfortable and then letting you make all the aesthetic swooping armrests you like: at that point, the chance that you will duplicate another person's work near-exactly suddenly becomes a lot more likely, especially if Chairmaker 2020 is a popular program.
In short, copyright law is currently almost entirely unprepared to deal with the coming legal issues surrounding 3D printing. Of course, if current trends in copyright law are any indication, Canada will come up with a legislative platform designed to deal with the implications of 3D printing approximately fifteen years after it begins to matter.