In my times using the Makerbot, there have been quite a few 'bad prints'. The platform skips, the extruder runs out/can't pull enough ABS/PLA plastic, warping. But ABS is expensive, and it is reusable. The same goes for PLA. I wonder how easy it would be to develop a system that melts and reshapes the plastic into long strings. Better yet, a system that goes with the extruder so that a bad print can be tossed into a funnel and reprinted.
I can't see why this hasn't happened yet! Maybe its a matter of time.