Today's Deke's Techniques explains how to magically remove unwanted people from a photograph. Crazy as it may sound, you can take anything that moves in a scene---a person, a car, or even a distended orangutan head---and make it disappear into thin air. Suddenly a crowded plaza or distant vista becomes altogether vacant.
http://www.deke.com/content/dekes-techniques-022-removing-people-with-image-stacks