I think the fact that, as Cory says, "The "derivatives-friendly" Creative Commons licenses allow amateur translators to share the fruits of their work, get friendly feedback, collaborate and gain reputation, encouraging them to do more and more work" is only the most apparent effect of CC on translation.
There's something more, and it could be so worth exploring and exploiting these side effects: first of all, the concepts of faithfulness and original text as are determined by strict copyright fade -- if I can make a derivative work, when I translate I must not submit to the style directions of the publisher who owns the rights for my language, so that I can translate in a more experimental way without having to abide to the translation-treason dichotomy.
The third effect I see (there could be many more), is strictly related to Cory's call for more translations into English: if I'm not a native English speaker, according to tradition I should never translate into English. But if my work is released under a derivative-friendly share alike CC license, I can render the meaning even if in an unsophisticated way and encourage native speakers to review and refine style. This could invert the widespread trend towards the diffusion of Anglo-American culture around the world, and favour the diffusion of cultures from non English-speaking areas.