I just resolved a copyright infringement issue with one of my images and wanted to report what worked for me.
I was contacted by a client who had been contacted by a fairly anonymous source (the email address was the name of an obscure turn of the 20th century author) who had found my image gracing the cover of a book on Amazon. The anonymous whistleblower was so good as to inform us that the "publisher" was using CreateSpace -- an Amazon company that facilitates self-publishing and fulfillment and the email address for copyright disputes. (I have a feeling it might be a rival "publisher".)
I clicked the link and there it was! After some research I tracked down the publisher's website. Their business model was clearly republishing public domain works -- a few dozen titles -- but several (especially dramatic works) with clearly recent photographs as covers. I emailed CreateSpace and informed them of the issue.
In the meantime I was weighing my options. The publisher was based in the UK, which I guessed would make legal action more expensive and lengthy. While stewing, I drafted a letter and an invoice – the publisher’s name and address was available from a Whois search on his website.
In about a day, CreateSpace wrote back telling me that they do not involve themselves in third party disputes, but would pull the book until the dispute was settled. They did give me the publisher's email address. Apparently they contacted him with mine, as well, because almost simultaneously I got an email from him. He pled ignorance and swore the title had been withdrawn from sale.
At this point I almost let him off the hook, since he had acted so quickly. But a couple days later, the book was still on Amazon, still showing for sale and still with my cover. I wrote back and included my invoice for a month’s license and a promise that if the book was not removed, he’d receive another at the end of the next month, as well as legal action. I got another very apologetic email saying that it was Amazon’s fault and that my invoice would be onerous to his business. I wrote back pointing out that his business model was publishing public domain books and that he obviously understood copyright well enough.
Long story short, a couple exchanges later, he paid the invoice in full. The image is still on Amazon, but a copyright infringement report has been filed with them, so I’m hoping it will be pulled this week. I do think there is some corporate behemoth inertia involved there, but we’ll see. He's scrubbed his site of the most blatantly stolen images (though many are still on Amazon -- some big names in theatrical photography, too -- but again, I'm hoping it's Amazon's inertia). There are still images of artwork... but trying to explain that, while the art on a Grecian urn may be public domain the photograph of it is not, is just not a lesson I feel like teaching.
The moral of the story – sometimes the invoice (with threat of legal action) route does work!

