Especially it can be usefull for the young creators. When you have no name and followers and your artwork would be published in a blog with a good auditory it can make you good money without long process of getting known. It's like to be printed in a famous magazine. And surely it's good for the mature authors that are good target for stealers.
There can be a system that will be able to track on what sites your photos has been posted and to decide to show it or not. If photo have not been paid there will be just a black placeholder insted of photo or something like that.