Pinterest has a market valuation of > 200 million dollars...
30%+ of its images are flickr images...
... 99%+ of which are "All Rights Reserved".
How many
... page views,
... new subscribers,
... and $$$
have the most-pinned flickr images generated for pinterest, with the author not seeing a single cent... not even having the satisfaction of seeing their popularity on pinterest reflect in their flickr stats?
And: Pinterest does not even have the decency to display the author name and license info next to the image.
Pinterest's business model is flawed; it is based on systematic violation of copyright. At some point, someone will start a class-action lawsuit and invite flickr photographers whose works got "pinned" to sign up, to reclaim part of that >$200 million pie.
In fact, this seems like a valid startup idea to me: Create a one-page website explaining to flickr users what has been going on. Do a systematic reverse image search to find out which authors have been affected and invite them to join.
Arrange with an interested lawfirm to get a % of their fee in exchange for delivering the list of potential plaintiffs.