LOST: Who is Jacob after all?!

«Since we first heard of "the Jacob's List", we have all been curious to know about this misterious spiritual guru of the "hostiles" (...)» (in 'many journals of Lost's loonies'. Actually it's on my journal. Or it would be, if I kept one)
Yes. I too, am a freak for the TV show "Lost". Some have already given up hope that its plot one day starts making any sense, yet I, never stopped reading theories, explanations and hidden informations, in my quest to fit all the puzzle pieces of the most compelling TV show since Twin Peaks (yes, I understand the seriousness of my claims and take full responsability of its consequences). The point of this post is to warn you that the 3rd season is at an end, and I would very much like you all to make this place a haven for your theories and views. Who is Jacob? What is the black smoke? Am I mentally challenged and a complete nerd? Don't miss out on today's Lost episode...