here's a theory:
If you look on wikipedia.com, it talks about jacob and his twin "Esau's birth.
http://en.wikipedia.org/wiki/Jacob
Its all related to christianity to some degree. The tale goes that the father has a magical present or something and he can only give it to one of his boys. Esau was supposed to get it because he was the elder son. But jacob and his mom tricked the dad into giving it to jacob. Ever since then esau has been jealous of jacob. He was supposed to get the island..not jacob. he can't kill him either. sooo thats why there is a conflict between the two.
back to LOST: Esau tricked ben into killing jacob because he himself cant kill jacob. he orchesrated all the events. Helped get all the LOSTies back on the island. He knew that jon locke was close to ben and a leader and close to jacob. So he made him go back in time to "kill himself" and get the LOSTies back(as christian remember?) this made john locke dead. So this means that esau can take over lockes body(remember he was given christian shoe??)
After taking lockes body his next step is to convince ben to listen to him. He took ben to the smoke monster(aka his own house) Remember ben didn't know where the smoke monster lived??? job locke did!!!!(aka the smoke monster aka Esau). He brought him in and he "disappeared" he changed pods into bens daughter and told ben to listen to john locke no matter WHAT(aka listen to esau). So ben now HAS to listen to john locke. Then john locke tells him to kill Jacob(because esau cant). So tahts what ben did!!!
The reason why Esau is the smoke monster is because someone killed him a long time ago. he was then trapped in that house with that soil on the ground.(can someone clarify who broke the soil? hurley or ben/john locke in season 1?) Anyways, After the soil got cut, esau can finally leave the cabin.However, he can usually leave as a smoke monster only. But now since the soil is broken, he can leave as a human being(in a pod). He pretended to be jacobs friend throughout the most of the seasons because jacob enslaved esau's body in the cabin. Now that he is loose, he wanted to get revenge.
Thoughts???