With regards to Pintrest's server fetching a copy of the original, it sounds like responsible caching to me. If it was just a link to the original, then their

With regards to Pintrest's server fetching a copy of the original, it sounds like responsible caching to me. If it was just a link to the original, then their server would have to take the hit to serve the image. Seems a fair thing to do to. Imagine a photographer runs his own little site. Has a bare minimum cheapo set up, because he is not Amazon. Now, imagine one (or more) particular high res image gets really popular. Well, it wont take much for his server to get swamped and possibly knocked off line for what ever reason, maybe bandwidth limits on the cheapo set up. I would argue (for now) that what is happening is not just fair, but responsible too. A user uploading is no more than a manual version of what the server does.