This was one of those episodes, where a lot was revealed that helped Lost as a whole.
We learn a lot about Ben during this episode. How he was blamed by his father for the death of his mother, until ultimately he sided with the hostiles to eliminate the Dharma people.
As he tells Locke he was responsible of the death of 40-odd people.
During this episode we also got to know that in fact Ben isn't the leader of the others, but he gets orders from someone else. And here we meet the mysterious Jacob.
Nobody knows who or how Jacob looks like. But we saw Ben getting extremely agitated when Jacob talked to Locke. This leads to very interesting outcomes in the future.