After watching the opening and closing scenes of The Incident, I assumed that we were watching two super-human men -- Jacob and the Man in Black -- who were equal and opposite.
However, after watching LA X, my opinion has shifted.
Because we now have confirmation that the Man in Black and the Smoke Monster are one and the same, and that he/it is capable of (very convincingly) impersonating the dead, it's entirely possible that the Man in Black was just another dead man whom the Smoke Monster was impersonating.
A square is a rectangle, but a rectangle is not a square: the Smoke Monster is the Man in Black, but the Man in Black is not the Smoke Monster
I think this would have a lot of implications -- Is the smoke his true form? Where is "home" for a smoke monster anyway? Had he previously tried and failed to find a loophole using other identities? Perhaps that of the Man in Black? -- but my brain is just too full and sluggish to consider it right now.