Some personal thoughts on piracy (warning - long post)

[Frontcannon]

Multiplayer, especially CoOp, needs coordination. Coordination needs communication, and communication kills atmosphere.

To make a MP-game truly scary, the communication would have to be fitted perfectly into the game environment, which means not using VoIP for talking to your friend, but using the game. The voices would have to match the ingame avatars / characters, which means they have a position in the game world, are affected by echoes and distance to the player.
It's still a pretty rough idea, but imagine listening to your friends voice as if he'd be an ingame NPC.. I think it could avoid the usual problems and actually preserve the game's original atmosphere.