Out of thin air? No, out of (currently) 10.574 Thash/s. You think that kind of computing power is made of faery dust unicorn-horn? Think again.
hard work to obtain something doesnt make it valueable.
this guy worked hard with his lawn mower:
http://www.youtube.com/watch?v=CIaCHqxdSXc&feature=feedfand he's funny, too, which got to be worth something.