Yes, over at Cartoonbrew, they seem determined to whip up a bit of contraversy over Avatar's casting of white people, devoting two posts in a row to the subject.
Being honest, I don't know all that much about the show but a quick Google image search reveals the main characters in Airbender to have blue eyes. And Wikipedia tells me "The show drew on elements from East Asian, South Asian, and Western culture". That's a pretty broad area.
It also tells me that it's "set in an Asian-influenced world of martial arts and element manipulation".
Why is it that it is impossible for Asia to be brought up in a western cartoon without martial arts? It is impossible. Just does not happen. According to western cartoons, the only reason for the existence of any Asian country, of which there are many and each one being different to the other, is to showcase Kung bloody Fu.
Seems to me this entire show is built on a stereotype. So why get your knickers in a twist when the casting follows more the blue eyes of the characters than the vague amalgamation of Asian cultures?