I saw this story about a photo used in a Virgin Mobile ad that acquired a photo from a Flickr user. The photo in question has now been switched to a strict copyright, but it previously existed with a Creative Commons license that permitted commercial use.

Outside of a model release, I think it's interesting to see a mostly clueful company "linking back" to the Flickr source in their ad per the CC license, and lawyers and Flickr license grantors mostly clueless about what that license means.