Detecting altered digital photos

Slashdot has a pointer to a a couple of articles showcasing Dartmouth Assistant Professor Hany Farid's work on detecting altered digital images. Apparently, he and his graduate student, Alin Popescu, have developed a mathematical model that can determine whether or not various common image editing techniques (cloning, averaging, resizing, etc) have been applied.

How is this related to Information Security, you may ask? For one thing, it may have potential ramifications for the admissibility of digital photos as evidence in a court of law. Also, and neither article mentions this, it sounds like it may also have the potential to help identify images which contain steganographic content.