This isn't a caption, but just a general comment on the photo subject matter. As much some might find GW pressing the flesh with what appears to be a communist Chinese official (in Chile?) distasteful, The People's Republic of China is a very powerful global player. Their factories are going full bore 24/7, they've got well over a billion people who can appreciate the western notion of freedom, hunger for knowledge and information, and they won't go away. Unless things go south fast, outright blanket hydrogen bombing the populated landmass of mainland china and Hong Kong is pretty much out of the question. Therefore they need to be negotiated with. And shaking hands is part of the art of negotiation. So I'll cut the President some slack.
Consider also that China now has the 6th largest economy in the world -- they've surpassed Italy. And, they are the second largest buyer of U.S. bonds, behind Japan, but ahead of Great Britain.