In order to sell the minerals, there must be a way to attain ownership.
How does one come to own an asteroid, or the minerals it contains?
A land grab under a single government is manageable. When there are 200 sovereign states, who decides which asteroids are owned by whom? First to discover? First to land? First to return minerals? Passed though a parsec I have rights to? Or perhaps you don't own the minerals until you cross low-earth orbit with them in your possession. Sign me up as an asteroid pirate.
If a company does attain ownership of an asteroid, can they sell the asteroid before ever landing on it? Will asteroid futures be traded on the CME?
If an asteroid is found to contain 100 tons of palladium, what happens to the palladium market? (Cha-ching! I hold put options on Pd!)
Ya, far more interesting....
Wired started a dialog with: http://www.wired.com/wiredscience/2012/05/opinion-asteroid-m...
Discussed ownership, but there is no answer.
The Economist touched on it: "The most important members of the team, then, may not be the entrepreneurs and venture capitalists who put up the drive and the money, nor the engineers who build the hardware that makes it all possible, but the economists who try to work out the effect on the price of platinum when a mountain of the stuff arrives from outer space."