cbreum maybe a crusader, but you are a sophist. You make the premise that USD needs those computers to stay alive. What you intently forget to say, is that those who have the resources (eg the money) to pay for the kind of computers farm needed to keep Bitcoin alive are just a few. So, these very limited group of people controls the game. And, as it costs more and more to keep the mining process alive, even those who actually control this won't have enough resources to keep all the system alive sooner or later. Added to that, and in 2016 it is a well known fact, global warming is no secret and we should not discard this as easily as some seem to do. So comparing banks with miners is pointless as banks does not create currencies, they manage them.