This is a spoiler only in the off-chance that my theory is right ...

I've come to believe that Alpert's band of mercenaries are actually a legion of the undead. I may be waaaay off on this (and I can't find a screen shot that supports this claim) but I thought I saw Rousseau toting a gun when he captured Kate & Sayid. So what if everyone who roams with him is undead? That might explain all the island whispers. It would even explain why this peaceful-seeming guy got Ben to gas out his entire camp - more legions for RA.

Too out there? I wouldn't have been bold enough to post this if we hadn't seen (dead) Claire & her ghost-daddy wandering around so casually.

I'm starting to think the whispers are also part of the time shift thats going on. Are they 'out of sync' conversations from the past or future?

Maybe Richards men have abilities from the 'original' inhabitants... Which i assume are the poeple from the 'foot statue' era

I've been thinking about wormholes lately. A wormhole can be loosely defined as a passageway between two arbitrarilly seperated points in 4-D spacetime. Technically a very distant point in 4-D can also be very close due to the folding of spacetime, thus a wormhole need not be very long. This close, yet distant, alternative area for the island, could explain the whispers. They're just a heart-beat away.