I admit I can see the need on occasion to scan and then print a replacement part for something that broke, but usually the times that would have been handy is because I can't order a replacement part.
3D printing is changing the world, but counterfitting shouldn't be a worry unless the counterfit is better than the original! who would buy a counterfit engine part? and who wants a counterfit toy?
that is why piracy is rife with media, pirated copies are now better than official digital copies, they don't have DRM, they don't have limitations where you can play them, and the quality matches that of streaming/DRM downloads..