This is a gorgeous Sam vid. It shows why his world "imploded". Why he might have had a meltdown after Dean disappeared. Why he ran. *guh*
On one level I can totally accept Sam mentally snapping and choosing to live in a "dream" world. A world that was safe and free of potential mistakes, but on the other hand ...NOOOOOO! You can't just NOT look for your brother Sam!
Also, (while I'm here and this damn story line just WON'T LEAVE ME ALONE!! DAMN YOU!) I wonder if Dean not trying to get Cas out of Purgatory is somehow tied into Sam not looking for Dean. If Dean was so messed up by the thought of failing to get Cas out surely the first thing he would do when he got back was to go mad looking for a way to get him out.
Just curious. Lots of little breadcrumbs are being dropped I think.