"Broadly, there are two ways to get the goodies back to Earth. The first is to attempt to mine a large NEA in its existing orbit, dropping off a payload every time it passes by. That is the reason for the search for asteroids with appropriate orbits. This approach will, however, require intelligent robots which can work by themselves for years, digging and processing the desirable material."
These asteroids will be a perfect place for malicious AI's to spawn...