As 3D printing becomes truly mass-market, people who want to print copies of objects will start attacking physical product patents as strongly as they attack software patents and digital media copyright today (strong, coordinated opposition to these grew only with distribution channels).
I'm not ignoring it -- people used to make mixtapes for friends and copy games on 5.25" floppies (see the classic "Don't Copy That Floppy" -- but only when online distribution became a reality did people start arguments of the nature that "IP should not exist on this category of entity."
