One more thing...
OMG, I DID NOT NOTICE THIS FIRST TIME AROUND!!!! skroberts queried if Sam's eyes flashed yellow in the final scene, and they did. OMG, KRIPKE!!! What are you doing?! You lulled me with Sam laughing and Bobby joking, and boys leaning lazily against the car with beers in hand, and then you throw in this! Are you trying to kill us all?!!!
MEEP!!!
So my earlier dithering about why Sam didn't get sick (either he's less scary than Dean or he's immune) is over. No more dithering. Sam's immune to a ghost infection.
MEEP!!!!!!