I'm going to have to watch it again before next week.

Let's see, we had John in trouble with Yellow Eyes and saving Dean in S1.
Then we had Sam in trouble with Yellow Eyes in S2.
Then we had Dean headed for hell for saving Sam in S3.
Now, it looks like we're going to have the boys pitted against each other in S4.

Why do I get the feeling that they're going to get together and kick all their asses? ;-)