Title and caption should be one and the same. The current situation makes me double-enter information every time I upload a picture (since I can't figure out any situation why I'd want them to be different), and that is really irritating.
More generally, I've been trying to figure out a use case where you'd want the information to be different, and I can't think of one. If there is such a use case, then the UI should be changed to make that use case more discoverable, perhaps by retitling the fields, or explaining where each one is used. Perhaps then the bug should be retitled something like 'media UI should explain the difference between title and caption so that users can take advantage of the difference'.
Maybe worth noting that flickr doesn't have this distinction, and it does just fine. :)
