In addition to the exclusive Bioshock DLC for the PS3, 2K Games Executive Producer Alyssa Finley uncovered some details on the game's trophy system at Playstation.blog. Finley said that the various unlockable trophies are to encourage players to experience every aspect of the game - from hacking to having "Brass Balls". Here are some details from her blog:

• Bronze Trophy - earned by doing many successful hacks and unlocking.
• Silver Trophy - earned by a "true explorer". The "Historian" trophy can be obtained by acquiring every single audio diary in Rapture.
• Gold Trophy - earned by finishing the single player mode in hard, without the use of Vita-Chambers, as this really puts the effort in getting "Brass Balls". This mode will make the game ask you, "Who's your Big Daddy?"
• Platinum Trophy - no specifics were given but it's meant for "those few who can stare down a Big Daddy without shivering."

Of course, there are more trophies available when the game finally surfaces this November for the Playstation 3.

Playstation.Blog: BioShock PS3 Trophies Confirmed, Detailed