Read one of the most thorough articles I've seen on the white-washing issue here. I love that the author contextualizes the book cover issue within the larger practice of white-washing in general, i.e. media images like Beyonce in an Elle magazine spread (I've seen a similar thing done with Aishwarya Rai and Halle Berry--and maybe Queen Latifah? All reps of L'Oreal, by the way), and the Avatar: the Last Airbender casting issue.
Great article, overall, go check it out.