All right, so I came up with a theory last night while I was willing myself to fall asleep.

I got to thinking, "why does Witmore want to find this island? What's so special about it?" (Then again, what ISN'T special...)

Anyways, my answer was time travel.

And then I got to thinking how Ben knows everything... how he could send Harper to talk to Juliette, even though he was being held prisones...

Anyways, my point:

I think Ben has "perfected" time travel. This is how he knows everything.

We know he lied when he said he was born on the island. And we know that, with "Future Sayid", he's off the island. But maybe that "Future Ben" is realy "Present Ben"...

And maybe this is why Witmore wants to find the island? Some how he knows...?

Anyways, that's my theory! :)