This is probably to try to offset Moore's law, by keeping the hash cracking difficulty in line with technology progrss. But it's funny how this works. If you think about Moore's law, it's basically describing the number of transistors on an IC, those doubling every two years. But it doesn't address expansion in the ways we use our technology. If new machines come out which allow us to stack even more GPUs into a single machine, performance capacity per cracking host will rise even farther than double per year.

One person estimated an 8-GPU cracking machine two years ago at about 539 billion hashes per minute. At 128k hashes for one password, you could make about 70,182 attempts per second.

But here[1] is a five-machine cluster from a year and a half ago with 25 GPUs. Its speed? 63 billion per second against SHA1. This results in 492,187 attempts per second. Assuming SHA256 is about 50% slower, this would be around 246,093 per second.

Some password dictionaries contain millions of words. But if your password is '0Password', it'll probably be cracked in a couple of seconds on modern hardware.

[1] http://arstechnica.com/security/2012/12/25-gpu-cluster-crack...