Well, you've just made a very good argument against using sponsor content.
Paid content is hands down the best way to go. With the exception of times it's not possible, ie, solo girl sites.
That said, I just build what I build and hope for the best. Even using paid content, you are going to run into times when someone else has sub'bed using the same photo set you have. The site uses whichever one, based on a multitude of things. (recognized submit name, first one submitted, any other of a trillion reasons)