But I can tell you a story in which these digital tattletales don’t help. Our PhotoShop expert goes in and strips the watermark. I’m no expert here, but it doesn’t seem all that difficult for someone good enough to make a convincing mash-up in the first place. If the watermark were opaque, that would have been a different matter, but it looks to me like just a matter of undoing an alpha-channel blend with a known image, which is both straightforward and deterministic.
But — says Corbis — that would be a DMCA 1202(b) violation! Oho! Gotcha now! The fallacy is the same one that undergirds many misguided spam solutions: adding another penalty for knavery doesnt, by itself, help you catch the knaves. Every time you stare closely enough at the DMCA, it winds up being either horrirfic or redundant.