
I told Wendy last night I had Lost figured out.
The island is a jail for the smoke monster. Jacob was the jailer, keeping the SM from leaving and wrecking the world.
Jacob kept the lid on Pandora's box, the apple on the Tree of Knowledge, the door to the jail locked.
The SM is Chaos, and Jacob is Order.
The SM is constantly trying to escape and manipulates people into doing things for him. Jacob pulls/pushes/gently nudges people to counter those activities. All the events leading to the Oceanic 815 crashing and the survivors living on the island were gentle nudges by both powers - the SM aiming to secure release, Jacob working to keep the jail locked tight.
Thus there is a long history of balancing between the two forces of SM and Jacob (hence the black rock, white rock joke). The SM thinks he has won and is seeking to escape (through manipulation of Sawyer, Ben, etc) whereas Jacob has already set things into motion to counter this, way before his death (luring back the Oceanic Six, time travel of the survivors, etc). The balancing will continue on forever, long after the series is rendered unto syndication.
It's all about balance!