I have been curious about this too. Unfortunately though, my guess is that it is very very tough to estimate due to the sheer variety of hardware that is being

I have been curious about this too. Unfortunately though, my guess is that it is very very tough to estimate due to the sheer variety of hardware that is being used. I am sure that a large number of people are still mining with GPUs which consume more power/mhash than ASICs. I came across someone last week who was mining with a CPU, I am confident he's not the only one.