I believe OP is not concerned about bogus chains, but imbalances in computing power. This is not a serious problem but it looks like one on the face of it. If a

I believe OP is not concerned about bogus chains, but imbalances in computing power. This is not a serious problem but it looks like one on the face of it. If a massive amount of computation suddenly went into computing bitcoins there are two issues you could be worried about. The first is that it isn't very fair. The reply to this is that the current balance of money isn't fair either, we just didn't get to watch it happen. And as people have said elsewhere, it's not reasonable to expect a currency to solve social inequality. The second is that, if the cost of mining a bitcoin goes through the roof but there is not enough economy to make money on transaction fees, then people will drop out of mining. However: difficulty is not automatically increasing, it's proportionally increased or decreased relative to the difficulty of the past two weeks. If it becomes prohibitively expensive for Amazon to mine for bitcoins and they drop out, the threshold will fall again. Either way there's always an incentive to keep it running, until the system is out of coins. (edit for clarity)