Another shot of this greeting is here.
My Comment: This is not the image that you want Asia to see from us. It is acceptable (to a point) to bow to the Emperor of Japan, the Saudi King, The Queen, The Pope, etc. .... but not to the head of the Chinese Communist Party .... and not when you are President of the United States.
What is infuriating is that it appears (in the AP photo) that Chinese President Hu Jintao is grinning at President Obama while he bows down. I guess he knows how silly this looks.
A prediction .... in the next few days this picture is going to be played out over and over again in China and elsewhere in Asia.