In a Memorandum to the Internet we posited the theory that the SmithsonianImages.Com site was artificially restricting the public domain by asserting copyright on images they did not own. Indeed, the whole point of the public domain is you don't have to ask for permission, yet the Institution had required each and every use to be vetted.
Since careful examination yielded substantial evidence that the images were indeed in the public domain, they were harvested and uploaded to Flickr, which managed to attract the attention of the relevant authorities.
[View 6,288 Images on Flickr]
[View the Smithsonian's New PD Photostream]