Well, over-the-top stereotypical, anway. Funny thing is, according to Stephen Ambrose, when he was doing all the research for all his various books on the subject, he found that the stereotypes were basically true. Most units had a Brooklyn guy, a Kansas guy, a Harvard/Yale/Ivy College intellectual all thrown together in the stew.
Anyway, COD3 multiplayer has these neat little touches, like the above audio which your "character" yells when he gets off a good kill, or whenever a sniper kills someone on your team you'll hear "Sniper! Get your heads down!" Or, when a grenade is thrown, "Grenade! Take cover!" So you don't have to worry about people on your team who never talk. I think it's cool, and more multiplayer games should do stuff like that.