From Carlton Cuse, co-creator of Lost, explaining why they're going to leave a few things still mysterious when the show ends this season:
To sort of demystify that by trying to literally explain everything down to the last little sort of midi-chlorian of it all would be a mistake in our view.
It all sounded like a cop-out until he put it that way. Now I totally approve!
Plus, of course, this approach keeps the door open for Lost specials in years to come. It's always best to leave that option on the table.