Well, marking the pictures as enhanced sounds like a great idea - but there's different levels of enhanced. Can one symbol cover "lightened up a little" or "cropped to remove trash can at edge of scene" or "pimple removed from left cheek" or "passerby removed from shot of family in front of monument" or "Uncle Al removed because he left Aunt Mary" or "new Uncle Pete added where Uncle Al used to be" or "Uncle Al and Uncle Pete having the shouting match we're sure they would have had if they'd ever been in the same room"?
I admit that when I use my digital camera I consider the process of checking the brightness and contrast an essential part of preparing the photo for an audience - and I've been known to take the negatives from my film camera back to the quick print place to ask them to do a photo again a little lighter or darker - especially when my goal in taking the picture was to show the play of the shadows on the water rather than the detail of the boat producing the shadows or whatever.
My personal dividing line (for myself - I don't know what sort of standards we should use for professional photographers or photojournalists or whatever) is probably in favor of things that make the original photo I was taking better - up to and including removing the guy who walked in front of the lens as I clicked. What I saw when I took the photo was (in my mind's eye if not in my viewfinder) properly exposed and nicely framed and didn't have a stop sign coming out of someone's head. (I'm getting better at really looking at what I'm seeing - but I still tend to focus on the subject of my photo and mentally block out the background.)
I have no problem with moving Uncle Pete around, and have done things like that - but I think that the result is something other than a photo. I'm not sure what - but it does make an interesting topic of discussion.
I'd like to see a special disclaimer on photos that are intentionally made to deceive - but I suppose "photo edited to support my world view" probably won't catch on....