Optical illusions are awesome. That cannot be debated. Ever. Some of them are used to be thought provoking, street art that looks one way from one viewpoint and completely different if you move. Some are just to screw with your brain, like many of Escher's famous pieces.
This one is used to make you want to buy Ray Bans. No, seriously. http://www.youtube.com/watch?v=dhuUhaNIWLQ.
So why do these things look 3D to us? Courtesy of our lovely brains, which like to detect patterns where there aren't any. Some awesome drawings with shading intact, stretching the perspective so that it would match the camera angles, and boom, things look like they pop off the table. Eyes may not be that easy to trick, but the brain interpreting the images is. After all, if we're used to things sitting on tables, why wouldn't the baseball be just another object on a table?
Advertising tells us sunglasses are the only thing that is real. Get ready for the paper apocalypse, everyone.