People don’t cross their arms for photographs on their own. It’s the photographers who ask them to do it, resulting in a pose that is supposed to show that the person is tough and uncompromising. It’s a lazy photographer that does it, though. A posed shot like that is easy but unnatural. Here are two from today’s New York Times:
Update: Here’s a third one from today’s Times, a picture of, incidentally, Louann Brizendine, who Mark Liberman at LanguageLog has been justly criticizing for her sloppy conclusions.