Here's the thing: Rice can indeed dry out your iDevice if it ends up taking an unexpected tumble into a pool, pond, or -- tech gods forbid -- toilet. That being said, this is not the way to do it. Leave your device off for as long as possible, and certainly until you're confident there is no more moisture left inside the device.
Leaving it on is not a good idea, but I have a feeling the photo was just taken for the effect. Oh, and the great macro with the rice grains.
[Photo credit: Steven Depolo]