[krapp]

It would be just as doomed as any other DRM scheme. You can't stop anyone from copying an image, removing any metadata that might be there, or even if they're clever, from cloning out a watermark.

[porsupah]

Reading the original quote, and assuming good faith, they're wishing for some system that would permit them to establish an image's owner.

If you don't take steps to strip out typical metadata, such is indeed already present, in EXIF and IPTC fields.