Mary saved John and John ended up a bitter, lonely paranoid hunter. Sam saved John and John sold his soul to save Dean. Dean sold his soul to save Sam and Sam ended up alone, desperate and vulnerable to Ruby.

I never actually thought about the deals John and Mary made mostly focused on the negative effects of the deals the brothers have made but those are excellent points :). As Ash said hopefully the writers will continue on this course rather than wimp out. But then with their insistence on portraying Sam in the worst light possible I still fear that Dean and his inability to move on from this vicious cycle is going to be the one proven 'right' in the end *sigh*.