To finish a thought I had last night while trying to fall asleep: Sam feels a lot less assertive of himself as a person in s2. As a result, the power dynamic between the boys seems noticeably unsettled.
My main point being, this season there's a lot more of Dean leading, Sam following (I'm only a couple episodes in mind you, can't remember if this shifts back again over the course of the season).
Now this could be either 1) the writers reacting to Dean's popularity or just wanting to give Jensen Ackles more action-hero-y scenes (I've noticed they're having him wave a gun around more often as well) 2) supposed to be read as a conscious decision on Sam's part. I think option 2 is cooler. At this point, we know Dean is spiraling and using their hunts as a means to feel in control of his life again. We know Sam is aware of this. So his stepping back and letting Dean lead could be a conscious effort to give Dean the space he needs to come to terms with his grief.
But unfortunately, this causes the power balance to shift. Where in s1 Sam and Dean felt fairly equally matched, working as a well oiled machine that didn't necessarily need a leader, now Sam's putting himself on the backburner to make room for Dean. And he's making himself into a bit of a punching bag in the course of it (literally: I forgot Dean turned their fights violent this early on, I thought the punching started later).
I just think it's an interesting turn for this particular character to take. Sam in s1 was mainly defined by being the free thinker, the one who broke the family's chains, the one who did his own thing, who was uncompromising in his wants. And now we're watching him adapt an incredibly maladaptive coping mechanism that's gonna haunt him for the rest of the series: He's minimizing himself and his own pain or grief in favor of watching out for others' (Dean's) wellbeing. I just. Ugh. Man...
