leastauthority.com (the Tahoe LAFS folks) are trying to promote the concept of "RAIC" (C=Cloud). I'm not sure what the status of the project is, though...
FWIW, we are happy to support this kind of use, and see our customers doing it in an ad-hoc way every day. We have s3cmd in our environment, and support it. As soon as their is a glacier complement to s3cmd we will put that into place as well, although with the strange traffic and retrieval pricing, I'm not sure how useful folks will find it ...