Quote: "I'll throw out another question. When taking a group photo, such as a baseball team or a school group for a yearbook, is it appropriate to photo-shop missing members into the final image?"
Yes, adjust the photo based on input from the team, manager, president, whomever is your contract. You are creating a photo from instructions of the promoter. Adding, subtracting, manipulating to orders -- no problem with that -- every one knows.
As for the other parts of this: My personal opinion only ...
As journalists, we are required to submit images as shot in the field -- no manipulation. Sometimes, editors will crop, manipulate minor corrections, but generally it's always assumed that the image in any journal or newspaper, magazine is direct from the camera, a recording of history. Journalists have been fired for changing an image -- one in particular in the news last year - cropped (or cut) a piece of his assistant's camera out of the corner of an image shot in Afghanistan during a conflict -- and he was immediately fired.
Fine Art: The image is what you make it -- the artist is in control and in my mind, no disclosure is necessary before, during, or after a sale, unless a buyer (or anyone) asks -- then tell the truth (I mean, why not if you are proud of the image) ... in the first place, most (but not all) manipulation is often obvious. If a buyer likes an image, buys it, it matters not how it arrived at its final destination. Where I would draw the line is non-disclosure if asked, tell the truth -- if it's a raw shot from an actual scene - say so ... if it's manipulated to a large or small degree, admit it. IF the image is for yourself, who cares?