I doubt that home 3D printers will ever be a serious danger for regular products. A user might print a case for his iPhone or something like that, but even the most simplistically functional objects tend to be far beyond what a home 3D printer can do. Even when a 3D printer can compete, it's often more expensive then the same product done regularly somewhere in China and shipped over here.
I think the copyright with 3D printings won't be with the big manufacturers, but within the realm of the hacker/maker crowd itself, people taking each others design without following the license and stuff that like. Wouldn't surprise me if some Chinese company would start mass producing a popular object without paying royalties either. But that's basically the same set of problems we already have with Open Source, music, films and even Youtube videos.
In general I consider home 3D printing rather overhyped, there is only so much plastic crap you can print and most people won't have any use for a personal 3D printer. Outside of the home, 3D printers are for more interesting, be it to create rocket parts or organ replacements, but your home printer won't ever be capable of that.