Over at the Official PlayStation Blog, Tommy Rydling, junior product manager at Battlefield 3 developer DICE, says that starting with the first post-release DLC pack called Back to Karkand (out sometime this year) all "full-blown" expansion packs to the game will have a week of exclusivity on PSN.
Interestingly, this move is the mirror opposite of what the Call of Duty series has done recently with the Black Ops DLC, where it has been available first on XBLA and then PSN (albeit for a full month before).
{GameInformer}