Here's what I think... The island itself is light and dark, good and evil. Ben is evil and communicates with that side under the pretense that he is communicating with the good side, and Jacob. He has held up this con for many years, but there are chinks in his armor. Fate has played well with Jacob recently, and has bought him a plane load of people to help bring the light side back into power, but Ben, realizing this, is trying to stop it. the Others are good, and always have been, but have just been following the wrong guy.
Jacob called out for help because perhaps he can only do good by having a relationship with someone who follows the light. Maybe the good guys are like jedi's and can see spirits who can guide them.. so what happened to Ben along the way, did his father turn him that evil?