"President Barack Obama plays peek-a-boo with Maeve Beliveau, the daughter of Director of Advance Emmett Beliveau, in the Outer Oval Office, Oct. 30, 2009." Credit.
Taken out of context, a variety of other captions would be possible. The Reddit thread was entitled "Obama bows to everyone."
Blogged because some of you will be interested to learn that the White House has a Flickr photostream with about 800 photos in it. These photos are classified as "U.S. Government Work" and thus are copyright-free:
A work that is a United States Government work, prepared by an officer or employee of the United States Government as part of that person's official duties, is not subject to copyright in the United States and there are no U.S. copyright restrictions on reproduction, derivative works, distribution, performance, or display of the work...