I think the ability to develop a commentary on images, and parts of them, is powerful stuff, Images can sometimes be more compelling and accessible than words. I used to teach a lot of art history, and I quickly learned to let the projected slides do the work: sequencing them carefully so that the conversation built on one will be amplified or extended by those that follow, was a fine way to get students talking. So, I'd add to the examples cited here, if I understand them right, more than captions: I think the real return on investment would be when some sort of threading functionality kicks in, like integrating annotation with forum functionality. Or? -B
