ok so we know that when llana went to the cabin she said that jacob wasn't there anymore and that someone else had been using it. i think it was mib,duh, but when ben and locke were in the cabin ben was pretending he was talking to jacob. locke turns on the flash light and things started moving and flying across the room, and ben got hit, then we see a man in a chair. i was thinking that the mib was angry because locke was not supposed to see him, because mib wanted to use locke later. maybe locke seeing him would have disrupted the loop hole that mib had set in place.