I don't think stealing it is the best way actually, botnets are pretty unreliable, and to have them doing computation would easily alert the people using the machines to the fact that something isn't right.
Maybe Obama could use botnets to create 'aggregate demand' as a stimulus package for computer hardware. The bots could just wastefully chew up processing power and people would upgrade, stimulating the economy. Sounds just as productive as all of his plans. How do you get a job in that Administration?
