Thought I'd start a thread for Theories.

Here's my first.

Jacob is Locke caught in some kind of space/time continuum.. Ben is following orders step by step that Locke has told him he needs to follow in order to get the island back into sinc with the world....and of course Jacob knows he is Locke but Locke can't know he is Jacob for the plan to work.

one of my theories:

The Orchid is a place where they can achive the task of moving the island, not in a physical sense but, move it in time/space.

Agree that Locke is the new Jacob. Also think that Aaron will be the new Locke someday.
I think that Christian speaks for Jacob because Jacob can no longer speak for himself since his time has come and gone, thus, the need for a successor. Locke has been the chosen one since birth but was not ready to believe in true purpose and so, Ben was special enough to be his temporary stand-in.
Ben is vindictive enough to have a plan to thwart Locke becoming the island's chosen son. Another theory I have is that Ben somehow trapped Jacob in time/space and is pursuing his own agenda which Richard alpert is attmpting to correct through Locke.
I wouldn't be suprised to see Ben in the coffin. That's just mho.