>...it would take a single GPU about a year to crack a password of average complexity with 500 iterations, and about 10 years to crack the same password run through 5,000 iterations.

>However, these numbers radically come down when a determined adversary also has other large-scale computational assets at their disposal, such as a bitcoin mining operation that can coordinate the password-cracking activity across multiple powerful systems simultaneously.

Wow. I'll bet Satoshi didn't consider this second order effect of the proof of work scheme. People who build energy intensive mining operations have the means and incentive to turn their mining operations on existing accounts when that becomes more lucrative than creating new blocks.