Actually, it's been my understanding they're NOT pushing it via 3G: A) because of the below from Amazon; B) because of other comments Amazon has made; C) because 3G "costs" them and Wi-Fi doesn't and D) there is NO Kindle with ONLY 3G. (Presumably this is one reason why they provide a download via PC: Someone who can't GET ON a Wi-Fi connection can download it.)
http://www.amazon.com/gp/help/custom...deId=200529700