Ridiculous article by a ridiculous blog. They acknowledge that the DMCA protects them and then proceed to explore whether what Pinterest is doing qualifies as fair use, concluding that they are probably not covered by fair use and therefore probably illegal.
This was one of my first questions when I first looked a Pinterest. I don't think it is ridiculous, and I'm not sure they are protected. The interesting question is, if they were to loose a court battle, would the court just require them to remove the image in question, or would there be larger implications?