When checking out someone who copied images from my site I also had a quick look to find out where else he was getting his images from.
I posted the image URL in image search and 8 Pinterest results showed up as similar images. The weird thing here was that the original image on the photographer's website didn't show up in the results. I had to click the image on Pinterest to find it. And of course, he has a "Pin It" button next to the images on his site.
It pretty much looks like this webmaster is giving all his content away. I'm afraid that a lot of webmasters are in for a huge surprise sooner or later when Google gives credit to Pinterest instead of the owner. Maybe it is logical in the eyes of Google's algo. If you find a certain picture 8 times on Pinterest and 1 time somewhere else then it must be clear who (which domain) the owner is.