Re:In order for nanomachine to create ne thing use (Score 1)

I've wondered about this overmultiplication effect, but from a different angle. What if fast self replicating nanos were launched at an approaching asteroid. Could enough nanos eat a whole asteroid, thereby remove a threat. I know that there are many factors are involved, but the idea itself is pretty exciting. Give them date by which to cease operations, launch them at armegeddon like asteroid, wait, watch gazillions of nanos burn up on re-entry. I could only think of 2 basic problems: 1.) make sure the stop timer is set right(wouldn't want them to re-enter and munch on earth) 2.) find some other earth saving labor for Bruce Willis and crew.