While trying to find something on the web on a totally different subject, I dropped into the following : http://www.theatlantic.com/issues/98may/photo.htm
. It is about digital enhancing of photos. Although it is a very long story and mainly about nature photography, it might give you some food for thought. I have lifted out two parts and copied them below :
1) "In 1991 the board of directors of the National Press Photographers Association (NPPA), noting that emerging electronic technology enabled "the manipulation of the content of an image in such a way that the change is virtually undetectable," adopted a statement of principle: "As journalists we believe the guiding principle of our profession is accuracy; therefore, we believe it is wrong to alter the content of a photograph in any way that deceives the public."
2) "About three years ago I led the industry in demanding from my agencies that they start labeling digital illustrations as such. They concurred and started labeling. Now most stock agencies around the world are following suit. I think the rest of the photographers at Jackson Hole thought that that was the most appropriate way of presenting the work. They also felt that digital enhancement -- darkening of sky, say, and other things that had been done in the past by printing techniques in the darkroom -- need not be labeled."