You can talk to friends (people you've exchanged friend codes with), and rivals (people you sent an invite to mid-game for rivalship) with the Headset. You can not talk to Randoms, but you can talk to people who were randoms before you rivaled them. .
Hell, there are no rules here - we're trying to accomplish something. -Thomas A. Edison
I have to wonder though, with the delay, if that will be removed if we see a FC-less CoD Black Ops... It seems that AV somehow broke down Nintendos defenses, and all the networking info we have on this game is several months old. There still is hope!
~~~~Frozen Primates and Polite Rodents make for really good bands~~~~~ "The extreme irony of life is that nobody gets through it alive"- a friend