if it's just little plastic objects well, that's stuck in the realm of knickknacks / Junk IMO. And I suspect most people will quickly get to that point after the first cheap 3d printer shows up.
It could really revolutionise some things, like home appliances. The little plastic latch on your appliance break? Print out a new one. The plastic flap that keeps your battery in on your digital camera break? Print out a new one. Suddenly a lot of devices might be much more 'repairable' now.