Giving attribution to imgur would be pointless as it is not a site known for original works. My guess is, the percentage of original images uploaded to imgur by the author is a small percentage.
What makes the connection between pinterest and flickr so interesting to me is that (if I remember correctly) A THIRD of pinterest images come from flickr, and pinterest thrives on using flickr's awesome repository of images against the law and the spirit under which most of the images were uploaded.
I believe I know why they are not hotlinking... if they did, they would immediately get a sh!!load of complaints from flickr authors about their images being used that way. (As anyone can attest who ever hotlinked flickr images on their sites, even WITH author attribution.)
If I were flickr, I would implement a feature "Your image has been pinned on pinterest!" with a notice that the views on pinterest will not register in the flickr stats, and allow the author to send a take-down notice to pinterest by pushing a button.
I meant that people upload pictures to Pinterest and they upload pictures to Imgur, but no one would ever worry about the images they uploaded to Imgur, because it's so anonymous.
I think Pinterest has managed to attract a different crowd from Reddit/4chan. For Pinterest users, it isn't so important to know that at any moment you can retreat behind a cloak of anonymity, whereas Redditors and 4chan users regard it as a fundamental human right.
I'm glad you commented though, I agree with what you're saying and I had no idea about flicker users having a history of people pulling their stuff. That definitely changes the game.
What makes the connection between pinterest and flickr so interesting to me is that (if I remember correctly) A THIRD of pinterest images come from flickr, and pinterest thrives on using flickr's awesome repository of images against the law and the spirit under which most of the images were uploaded.
I believe I know why they are not hotlinking... if they did, they would immediately get a sh!!load of complaints from flickr authors about their images being used that way. (As anyone can attest who ever hotlinked flickr images on their sites, even WITH author attribution.)
If I were flickr, I would implement a feature "Your image has been pinned on pinterest!" with a notice that the views on pinterest will not register in the flickr stats, and allow the author to send a take-down notice to pinterest by pushing a button.