Sony has finally confirmed that starting with Resistance 3, they will be introducing the PSN Pass as well as single use codes for online play.  For games that are included in this program, the game will need to be purchased new in order to redeem the code found inside for online play.  Any users who purchase a used game and try a previously activated code will be unable to access online play. Alternately, players may purchase the PSN Pass, which will allow them access regardless of how they purchased the game.

Sony exes have stated: "This program will be game-specific. Games that are a part of this program will include a single-use registration code that grants the account holder redeeming the code full online access for that title. This is an important initiative as it allows us to accelerate our commitment to enhancing premium online services across our first party game portfolio."

In other words, in order to combat the used game market, they'll be restricting online usage and ensuring that only 'full paying' customers have access.  Could this be the first step toward always requiring a unique code simply to activate the game for regular, offline play on consoles? We sincerely hope not.