BC2 does something like this, where if you sprint, you can't aim your gun, and when you come out of sprint, you have to wait like a second before your gun comes back on screen and you can shoot again. I HATE this feature - It's like,
"well, you can run. but we're gonna punish you for it." Why? It's running? Not exactly a wallhack or an aimbot...
They apparently aren't giving weapons weight that affect movement speed, so holstering weapons to move faster seems pointless.
http://www.splashdamage.com/forums/showpost.php?p=203541&postcount=49