With all the tagging, captioning and other meta-data that goes into digital photos these days, I think it's about time an image format included more detailed meta-data. We have the ability to store some specific meta-data in the JPEG format, but if you've identified the faces in a portrait (say, on Facebook) that information is stored outside the image file itself. If you make a copy, the names don't come along for the ride. If the names were stored inside the file, any copies would still contain that info, and no external database or program would be needed to associate them together.
Mokalus of Borg
PS - I know there's a "JPEG 2000" format with different meta-data standards.
PPS - I'm not sure what kinds of meta-data can be stored there.