The Soft Grey Line

When is a photograph no longer a photograph? At what point is an image so "pimped out" that it leaves the realm of photography, and enters the province of illustration? If you clone a crumpled beer can from of a landscape shot, is it still a photograph? If you merge multiple shots into a single image, can you call it a photograph? If you heal all the pimples on your model's face, is it still their photograph? Where is the soft grey line between photography and illustration, and when do we cross it?