Co-op has been confirmed, exact form is still sketchy but people have played a three-person 'get to the other side of the level while fending off a horde' game.
I don't care about this at all, this whole coop hype of late is completely wasted on me and I don't think the MP will last. Ah, it'll probably be fun for a month or two.
linky [http://kotaku.com/5228723/hands+on-with-uncharted-2-multiplayer-3+player-coop]
plus footage of the MP [http://kotaku.com/5229694/uncharted-2-among-thieves-multiplayer-in-action]