The only reason for Dean's actions that I can think of is that he's trying to be an ass so that Sam won't miss him so much when the year is up. Stupid and pretty unbelievable, but I guess even TV writers can be idiots about reading their own characters sometimes.

Since Sam called him on it at the end though, I'm hoping that we'll see a turnaround next episode. We'd better see one, or it's going to be impossible to enjoy the show anymore.