Of course if were talking about a 3d printer that can print me up a soda or an iPad that's a different story. But, 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.
Two- Competitive forces will favor companies which support this approach.
Kinda like open source won the desktop? No wait...
For things like appliances most manufacturers already sell replacement parts for cheaper than you could "print" them yourself, without the problems associated with printing it yourself.
For things like consumer level electronics, the manufacturers could sell replacement parts, but they'd prefer people replace the entire item. If the camera manufacturer won't sell a replacement flap, it's unlikely they'll give out the original CAD files for people to print their own.
In terms of the process, sure. But the product is vastly different; '2D' printing just generates a new encoding of the same information you've already got stored electronically, and when everyone has PCs and smartphones and tablets, a physical encoding of information is rarely a necessity.
But 3D printing actually creates a functional physical object that corresponds to a design; it's not merely a re-encoding of the information itself, so there's a huge value-add with 3D printing that isn't at all present in document printing, even if the current iteration of the technology is limited to producing small-scale uniformly plastic parts.
Or alternately how long will it take until we can print an iPad?