Asteroid mining is one of those things that comes into and goes out of fashion regularly and quickly. Here's a little blurb from Wired about its economic viability, and it plays in with my ongoing rant about how Space should be a commercial concern first, and a scientific one second. Worth a look-see if you've never thought about this, then come back here and we'll chat.

http://www.wired.com/wiredscience/2012/04/planetary-resources-asteroid-m...