Depending on how good our calculations are, it might be worthwhile to put some of those asteroids into earth orbit (make the margin of error such that if the calculations are off, the thing doesn't achieve orbit, and falls out of the solar system or into the sun). Having that kind of raw material delivered to the doorstep might make the difference in whether it was cost-effective to mine or not. Some of it might come down the gravity well, but I could see a lot of it staying right where it is, and being used to expand our space presence, or build ships.
I agree--but they better start with some small ones until they get the hang of it.