Episode 32: The Other 48 Days
In the flashbacks we learn that Shannon's dad died in a car accident and, when she is in the hospital, Jack walks by her. We also learn that Shannon's step mother doesn't like her and cut's her off from all financial resources.
Personally, I'm glad Sawyer didn't die. Not because I like him (I don't), but because it would be so obvious if he did. We knew someone was going to die; even a 5 year old could tell Sawyer was playing dodge ball witht he Grim Reaper. The writers know that the viewers demand twists and turns. Shannon getting killed was a pretty good twist. Ironically it is now Boone and Shannon that have been killed off from the show. When Sawyid saw what happened with Shannon he was visibly shocked; not just because of her being shot but because he can see the people from the raft standing in front of him. It's also interesting that Walt appeared to Shannon right before Ana and her posse, including Michael, meet up with her. Michael and Walt missed each other by seconds.