this may be a totally weird idea, but
if the whole thing comes down to good vs. evil, heaven vs. hell....etc..... could that make Desmond the Archangel Michael to Jacob ? (if Jacob represents God??) It may seem far fetched, but think about it. If he looks at Locke as "the devil"....last night at the end he seemed to want to get rid of him pretty good.....
Also, Desmond seemed determined to get Libby and Hurley together so he'd remember. It's almost as if Des is the key to everything fitting in place. (and he's just the cutie to do it too !!) But the Archangel Michael is "The Prince of Light" who is "patient and kind". what is love if it's not "patient and kind" ?

We'll have to see if Des gets anyone else "back together" to find love. But it seems like the forces of good and evil are priming for a battle to the end.
you probably all think I'm nuts, but that's my theory !

this show is a mind blower !!!