The Cult of Rapture, 2K Marin has posted a Q&A on BioShock 2 multiplayer. First of all, on all platforms, the game doesn't have distinct ranked and unranked multiplayer options. All public matches, including those played with friends, will be ranked and posted to leaderboards. Meanwhile, private, invite-only matches will not post to leaderboards. The game will also keep friends on the same teams and employs a matchmaking system to find opponents of similar skill levels. Also, the game does not include an option to kick troublesome players. 2K Marin suggests that players report any cheaters and griefers, quit and find a different match.
And now for the big one: BioShock 2 does not support dedicated servers or LAN play on any platform. According to 2K Marin, the development schedule didn't allow enough time to create a solid multiplayer component and implement dedicated servers and LAN play. The site reads, "We chose to spend the time we had creating a solid game foundation and unfortunately that did not include LAN play or dedicated servers." So there you have it.