*Spoiler Alert: If you haven't yet seen the season 5 finale of Lost, don't read any further!*
I personally enjoyed the season finale of Lost. I thought it answered quite a few questions, yet, in true Lost fashion, brought up just as many new questions.
One of the biggest questions, of course, is the identity of Jacob's enemy. I've seen a few theories on the internet, and one of the most prominent is that he is the Smoke Monster ("Smoky.") I think that is a credible one, and even if he isn't Smoky, it could be that Smoky is an ally. One thing that I think is pretty obvious is that he is the personage of Christian Shepherd seen on the island since the crash of 815, and he may well have been many of the other ghosts that have appeared to people throughout the show. Another theory floating around is that Jacob's enemy
(some people are calling him Anti-Jacob, some Esau, from the Biblical story) can only appear as people who have died, and the corpse has to be on the island, which is why Locke died and his corpse was put on the plane.
Anti-Jacob obviously went through some elaborate measures to orchestrate this "loophole," and it's interesting to go back and look at some of the things that could possibly be attributed to him.
I have another theory that I haven't seen discussed anywhere else. It is evident that Jacob knew at some point that Anti-Jacob was orchestrating these things. Otherwise, I don't think he would have asked Ilana to help him. I originally assumed that when Bram and several other people kidnapped Miles and tried to persuade him not to go to the island, this was Ben's doing. However, seeing him with Ilana convinced me that this was Jacob's doing.
If Jacob knew anti-Jacob was orchestrating something and suspected the connection with Locke, it's possible that he sent some of the losties back to 1977 in hopes that they would, in fact, change history, so that Locke would never even go to the island in the first place. Of course, we won't know if it even worked until early 2010! Anyway, it seems logical that this could be Jacob's failsafe, in case Anti-Jacob moved against him. He would basically be able to get a "do-over."
I know some of my readers are also Lost fans, and I would love it if you would post some of your theories on the episode here.