Theory: there are 2 monsters on the island. theory: one of said monsters is jacobs nemesis. the other monster is jacob.
In the episode "left behind", Kate and Juliet come up against what is seemingly the Smoke Monster. We are given a POV shot just like in the 1st season. Why wouldnt they show the monster in one scene but then show it in the next. what is especialy wierd is that the monster seems to be taking pictures of Juliet and Kate,or is just shining a bright light at the two. The only thing like this that we have seen so far and since is the monster judging both Eko and Ben. But still, why wouldnt they show us what Juliet and Kate were seeing? Perhaps the smoke monster is Jacobs Nemisis, since he was wearing black and can take other peoples forms. And i do recall Locke saying "i looked into the island and what i saw was beautifu" or something to that effect. Since Jacob is being seen as a contrast to his nemisis he would be a white monster, perhaps. and that is why we did not see what the characters were seeing. and in both pov shots i swear i could hear a stomping like noise, maybe the jacob monster has feet? maybe jacob is the foour toed statue(jusk kiding)