[IMMentat]

The only time I have seen prone be effective in a game is for hiding under a bush in BF3, camping in a corner with your legs partially through a wall in BF3 and in Operation Flashpoint where if you were not crawling everywhere you were dead to people the other side of a valley, on top of a hill, or looking out from under some neutral shrubbery. In every case it either turns fights into a game of hide and seek or gets you killed, especially in a game with massed airchav looking immobile squishy targets.