Hiding the fact that I:
1. Added a moon where there was not one before.
2. Cloned out significant objects because I was too lazy to be there when the object (like a car) was not there, or I was too lazy to compose it differently. For example, moving around to use a bush to hide a car.
3. Added a color that was not there. Or I cranked up the saturation to make people think I witnessed an awesome sunset when in fact I didn't.
It comes down to honesty. Art is what you make it. If I tell people that I wanted to insert a giant full moon in the middle of the sky at sunset in a wide-angle shot, just to make a surreal scene, that is fine. But if I tell people that I saw that scene, I'd be lying and therefore 'Photoshopping.'
Now, I make it a habit to carry around my camera with my most recent shots still in the camera. I show people the shots in the back so that they realize that what they see on my website and in a print is what I see in the back of the camera. And after I take a shot, I look at the back and compare it to what I see with my eyes, so when I get back to the office, I can process it correctly. Of course, sometimes the back of the camera does not look the same, so I remember the differences.
What do you tell people when they ask: 'Is this Photoshopped'
Here is a very thoughtful blog post (and some good replies) by Guy Tal on the subject.
patrick at patricksmithphotography.com