We're a bit late on this one - but better late than never. Infinity Ward has released a sick new video detailing the multiplayer gameplay session.
Those guys were destroying. Needless to say, MW2 is going to be awesome.
Those are personalized nicknames, as clarified in several "break-downs." YouTube the title of the video + breakdown to find out more... beware, some of them suck.
Cool, notice the text above the names of people he kills (clans maybe?), one of the says "Boom! Headshot"