sorry if this is already implemented or is in the pipeline but if you refer to images hosted by imgur, ie...on forums or blogs, the hotlinked images contained a backlink which says "Hosted by imgur.com blah blah" under that image. I think this will be a cool feature which should aid in the aspect of SEO because basically hotlinking is a wastage to our bandwidth so if we can't monetize it, we take advantage of it.