Now that I look more closely it seems they're using custom hardware with a much lower power draw...
http://www.butterflylabs.com/product-details/
One board draws 80W at maximum load and does 832MH/sec, or about 0.1W per MH. You'd make about $3/day revenue and pay <40c/day for electricity.
I remember reading something about rewards for solving bitcoins going from 50 to 25 sometime later this year, so your potential income would halve. Still profitable, but it would probably take over a year to break even. Too risky.