I don't know for sure but this pre-release interview it says they dropped it. Would be cool though, wish more games offer this, I know Halo 2 does but even that forces you to play in un-ranked games.
if u have a guest u have to play unranked but if u got 2 profiles on one xbox u can do as u like, buti dont think u can do that on ps3 its a real shame tho