How has image manipulation changed the world?`

My girlfriend runs a small business retouching photos of models.  It got me thinking how being able to retouch photos has changed the requirements for being a model.  

In other words under what conditions can one be a model pre versus post Photoshop?

Another way to ask the question is, "What cannot be replicated or corrected post shoot."

Cannot be: Bone structure of face, 

When will models cease to exist and cloths are digitally pasted onto avatars?

Here is an article on the impact of photoshop?