GamesRadar - Why co-op can be a terrible idea.
So, F.E.A.R. 3 (I’m not calling it F.3.A.R. until Warner Bros. send a gang of samurai around to make me) has co-op then. Yay! Co-op! It makes everything better!

Or so goes the logic of the woefully misguided. Because it actually doesn’t. No, while it’s good in the right place, co-op just for co-op’s sake is more than capable of ruining what would otherwise be a perfectly pleasant experience. Like a cheeseburger at a wedding dinner. And right now I'm really worried about the effect that it's going to have on F.E.A.R. 3. Here's why.

Co-Optimus - Co-Op Play is the Future of First Person Shooters.
I think it's quite good to hear that developers are realizing that gamers truly desire co-op play in their games. Do they, or we, demand it? I think that's a bit strong. But when you design a game that for all intents and purposes appears to be cooperative and it's left out - that's when we get in an uproar.