Physics of the game - and in FIFA 08 on next-gen, they are incredible. A ten-page booklet was produced in-house at EA Canada to describe how shots on goal needed to be calculated by the engine, and all of it was programmed into the game. The velocity of the player's foot, the spin on the ball as it approaches the player, even something called the Reynolds Effect all adds up to where the shot goes (for the nerdy among us, the Reynolds Effect is where the ball is struck so hard that for the first ten yards or so no spin is applied to the ball, but once the ball goes past a certain distance, the ball will slow enough for the spin to take affect and curve as you want it to - got a headache yet? I have, can I sue myself?). So if the ball slices off a foot, you won't see a perfect shot - the ball will roll dejectedly to the corner flag.