Shannon's father died suddenly - this set her on a course to travel the world. Theory: Jacob, is an evil SOB. He killed Shannon's father.
Recall: Jacob prevented Sayid from getting hit by a bus, but it was okay for the wife to get run over by the speeding bus.
Jack was furious when his wife left him for another man. The other man was Jacob!!!!
Ben brought Locke to the cabin to meet Jacob. Locke heard 'help me.' Theory: the voice belonged to the smoke monster. Which implies that maybe Ben was communing with the smoke monster all along instead of Jacob. Or maybe Ben had no idea that the smoke monster resided there.