I was never truly happy with that picture, so your thread got me thinking how to explain the energy requirements in a different way:

"If you had a computer that could do those calculations within a human's lifetime and were the size of the earth or smaller, and you actually somehow had an energy source to power it, as soon as you'd turn it on, you'd turn the earth into a supernova."

More detailed explanation in a more technical thread about it:
https://bitcointalk.org/index.php?topic=5216788