ONLY "Hack" Ive seen was a russian sniper laying down on a bridge, head and rifle sticking underground, shooting enemies on the other side of the map as a result of being able to see "Everything".
rest of the "HAX!!! HAX!! HAXOR!! CHEATER!!!" Rants are a horrible side effect of the nasty COD releases.
Trust me, everyone will know if someone is hacking.
Besides its quite hard to beat PB i belive.