Way to overreact, but that's not what I was referring to.
What if, in June 2010, I decide to play some TDM on MW2, then my buddy who is in the same party as me, decides to play some Hello Kitty Island Adventure. And then another buddy, also in the same party, wants to play Yaris. I would rather talk to them, but won't be able to, because of this party chat limitation that MW2 has.
Like I said, I won't see it as a problem within the first few weeks because all of my friends will be playing MW2. Later on though, it will be since I party chat with my friends on a daily basis and we don't always play the same games.