Sounds like the eventual goal of the Reprap project. "RepRap is short for Replicating Rapid-prototyper. It is the practical self-copying 3D printer" - See http://reprap.org/ for more info.
That's not surprising, since MakerBot founder Zach Smith is a RepRap contributor and also runs the RepRap Research Foundation (http://www.rrrf.org/). MakerBot's fabricators are based on RepRap designs and software, and they also sell RepRap parts in their store.