Incidentally, I think 3.23 Jack is also suffering from the same 'curse' - the inability to die - hence the island (if you subscribe to this idea) prevented him from jumping off the bridge by causing a car crash, which prompted Jack to change his mind.
I think all of the Oceanic 6 are or will suffer from the same 'island protection' (i.e. lack of freewill). The island wants them back, and so the only way to end their misery is to go back..(fate)
What insterests me is the man in te coffin - he was able to 'die' (unless the coffin is empty and it's a ruse ala Coopers fake funeral) - so why didn't the island prevent him from dying off-island?
Possible hints at it being Michael..and since he came back like the island wanted, he was then able to kill himself since the curse (if you will) was released..
(just musing and throwing things out there..
)
EDIT: of course, i'm
assuming coffin-man was also someone from the island..