I read an article over on Luminous Landscape that talked about how you just can't judge a camera without considering physical prints. While I won't attempt to dispute that for fine art purposes, or many other applications, stock photography in particular is an area of photography that is totally focused on "pixel peeping". Images are taken, processed, uploaded and sold with no printing on the part of the photographer. In many or most cases the image sold won't even be printed - if used in a Powerpoint, web page design, etc. In many other printed cases the quality of the print would be minimal due to output size. Certainly there are those who would ultimately print a brochure, annual report, magazine or art to hang on a wall. Those uses would be more demanding, but again except in the art cases the ultimately image quality would be limited - and the image supplemenatary.
On the other hand, stock images ARE reviewed by editors at 100% magnification. In that sense, the actual pixel level performance of cameras is much more important for stock photography than other uses. Not to say that it is of no importance, but a person buying from a thumbnail (or 800x600 comp) isn't even given a good example of the work prior to purchase.
© Photographer: Bradcalkins
Demanding 100% pixel level performance be of utmost importance does not really advance the art of photography, but it is a valid way to evaluate a camera if that reflects your end use... How many stock photographers ever truly appreciate or even need to know about the fine art of printing?