Modern Warfare 2 originally planned CO-OP

We are all looking forward to Modern Warfare 2, any news of what they wanted to do or didn't do catches my interest. A website named VG247 revealed that MW2 was originally going to have a CO-OP feature, and even though I don't mind they cut that it did make me think about CO-OP in video games today.

Personally I am glad they didn't include CO-OP in this game because I wonder if CO OP ruins a game sometimes, since most games don't set up harder difficulties if it senses more than one player. I saw this a lot with Halo: ODST, the game is a lot more time consuming when played alone.

I really think CO OP needs to be left out of a game UNLESS they design CO-OP where each player is on his own and does things where it assists the other player. A good example of this is the Gears of War 2 co-op which made you dependent on the other player.