I didn't explain myself for #2 very well... I can imagine a setup where a bot is monitoring the exchanges for the current BTC price, and perhaps (if such data is exposed) the market depth at and near that price. Then, monitor the Amazon spot price for GPU instances (if Amazon makes GPU instances available at spot rates, otherwise use their fixed price). At some point, the cost of BTC in USD would be greater than the cost of EC2 compute hours in USD required to obtain coins, in which case ramp up EC2 instances and get to work!