It is quite common to adjust digitial photos. In fact the camera has all sorts of processing it does on photos based on your settings. Being able to minipulate and adjust an image digitally is one of the great things about digital photography. Of course, usually the purpose is to make the photos look better.
I wonder whats wrong with the Yahoo editors eyeballs.
But the photographer or his agency should be the one approving of any manipulation of the images. Yahoo does not get that "right".