45,000 doesn't surprise me particularly, for Dan.
His cameras are tools for work. A D800 would be something one might use when large numbers of exposures would be appropriate.
Most likely it just takes one look at one menu or report using software for him to tell how many shots he has taken.
The small amount of output I have seen from a D800 was quite impressive - I am sure it is a well appreciated tool in the hands of those whose work requirements are well matched to it.
I wonder how many shots were taken by accredited photographers at the 2012 Olympics? I wonder how the number would compare to the number of frames of film shot at the last Olympics where film was the major medium?