After seeing how Locke's keeping Ben alive, it made me think of Locke's vision in Further Instructions, where Boone is pushing him around the airport and tells him that "One of these people need saving". As they scroll around the airport, Boone discounts all the survivors, but when they flash to Ben as the security guard, Boone says nothing.

Could it be that his vision hinted at what Locke's doing now? That would be some crazy foreshadowing.

There does seem to be really good reasons to keep Ben alive...the trouble is, the other losties aren't aware (or not as aware) of the weirdnesses of the island the way Locke is, thereby making him seem crazy.

I don't remember the connection with Ben in FI, but I remember the scene of Kate and Sawyer with the luggage and Boone saying something like "You cannot do anything for them, not now".