Check out the discussion on the Madisonian
blog as to whether Fairey's use of Garcia's photo for the Obama campaign image was fair use and whether Fairey's photograph was entitled to copyright protection at all (often referred to as a "thin copyright" - where there is not much original copyrightable expression in a particular work)! The blog author asks for feedback from photographers on these issues.
Compare the discussion at the Art Law blog
and the linked discussions there. Lots of questions, but no answers yet.