Those fpga clusters that he speaks of were paid for by other projects, and would otherwise sit idle earning nothing between major projects if not for Bitcoin.
I would imagine that whoever owns such hardware has some real use for it which he expects to profit from, despite the large initial costs. Bitcoin-mining with these clusters is profitable right now, but since such hardware power can easily be used (and sold) for other profitable projects in the industry, the threshold for them is most probably not electricity cost, but the next most profitable project the hardware could be used for instead.Don't forget, that with all the home-brew GPU mining rigs only electricity cost is the limit because their computing power can not easily be sold for anything else. If difficulty jumps up, the profitability shrinks for everyone - even those with the most powerful hardware.
Another factor is, that we have a global competition for energy prices and I am pretty sure someone here has access to cheaper electricity than whoever operates those clusters.
Last but not least, GPUs are getting faster and more efficient as well. Due to the much larger market and the very low hardware costs compared to FPGAs or ASICs, the advantage of the latter two shrinks continuously and the cost to upgrade them to the next better hardware generation is vastly greater.
FPGAs and ASICs are by far not the most imminent danger for Bitcoin so I think we should all just relax a bit, congratulate cypherf0x for his current advantage and upgrade our rigs with Southern Islands when they are available.
Everything's going to be just fine
