Creative Commons search index breakdown:
It appears that people licensing audio have chosen to offer more liberal terms than average while those licensing still and moving images have chosen less liberal terms than average.
And THAT, my friends, is VERY telling. VERY telling indeed. I'm looking at you, "the music industry".
(This also make me think out loud about the dichotomy between the aural and the visual "brainframes" and how we, as a culture spurned on by electricity, are moving from the latter to the former.)