"Ethics in the Age of Digital Photography"
A good article here. Wish it had pictures.
The National Geographic flap about the altered cover picture of the Pyramids was a major one for the magazine, and although the motive was pure, they swore off all forms of manipulation after that. In recent months, a photographer submitted photos under false pretenses, and when they later found out, the magazine published an explanation and apology. One assumes that particular photographer will not darken their doors again.