Has anyone noticed the signature monster sound that precedes Flock. Sounds eerily similar to chains being pulled across a rung, like a leach. It reminds me of the whispers from seasons yore which usually preceded the others, or in some cases a apparition or projection like Walt appearing to Shannon. (these 'ghost' appearances I believe were Jacob related/influenced. when a 'ghost' appears and no whispers occur it is MIB influenced)
It almost as if these two sounds define our two mysterious brothers, like the black and white clothes they wear. Some could argue the whispers have yet to be associated with Jacob however his agents, the others, walk with his call sign.
If this a game then the island is surely the board on which the game is played. I think the whispers belong to those pieces or players who have been removed, killed and to some extent claimed by Jacob.
If the scales tip in his/her favor.
To support this theory when Kate jumped into the pit to avoid the path of the smoke monster in Sundown, the sounds of wailing souls or screams could be heard (and to a lesser extent seen based on the shadow and light movement as it passed).
A symbolic representation of light and dark, good and evil, heaven and hell.
The whispers are the voices of the dead who have been claimed by Jacob. They act as agents who work on his behalf (for lack of a better analogy). An action similar to MIBs except MIB inhabits the souls he's claimed. Those whom Jacob have claimed retain their souls and act freely.
Not sure if this theory has legs or was previously posted. Thoughts?