I daily see wps that have been stolen from 500px, and not been given any kind of source. And yes, stolen, because most of them have copyright on their images.
In my opinion, if you are going to go to a photographers page and steal their photo, why not give credit by adding source to that image?
This is a issue that needs to be addressed. I am self a photographer active on 500px, and I surely don't want anyone stealing my pictures. What do the rest of you think about this topic?