The images that are displayed on Pinterest is on pinterest's server so I don't care about them stealing bandwidth from Pinterest. As long as they don't steal mine.
So what about the other social media sharing sites that are also image sharing sites. Don't know much about them but see some of my images on weheartit, indulgy. I am sure there are others out there I don't know..
On Facebook and tumblr images are pretty much being shared all over too.