Biden is perfect for the job of designated leaker. He works in an administration that spends half its time patting itself on the back and the other half trying to get the media to do it. Plus Biden, unlike the other suspects, has a vested interest in pumping up Obama's reputation as a strong leader because it'll keep him in the vice president's mansion for another four years.
One more thing. Remember when spokesman Jay Carney misspoke the other day? First he said "the Obama administration" wasn't responsible for the leak. Then he caught himself and said "the White House" wasn't responsible.
Though it's only my opinion, I bet Jay was actually telling the truth. It's not the White House that's been leaking. But if I were doing the investigating, I'd have someone take a very strong look at the plumbing in the vice president's house.