Flickr implements Pinterest code to block pins of protected pictures [updated]
According to Venture Beat, Flickr has implemented the new Pinterest security feature that does not allow Pinterest users to "pin" copyrighted or otherwise not-to-be-shared pictures on the Pinterest service. (via Techmeme)
If you have a website or blog and want to block or encourage "pins" for your pictures (depending on your disposition to this new thing), here is the Pinterest FAQ page with details on how to do that.
Just like most new disruptive things that come out of left field on the internets, there are almost always pros and cons, and a savvy photographer is one that maximizes the pros and minimizes the cons. For example, depending on a photographer's particular strategic and marketing circumstances, Pinterest could be a good source for viral promotion.