Here is a thought..... Jacob is real, and Ben can SEE him, but he only pretends that he can hear him. So, he goes around telling everyone that Jacob only speaks to him....when he doesn't at all. He thought perhaps Locke could also see him since he is special too. However, Locke couldn't see Jacob, but he could HEAR him. That would be a whole ying and yang kind of thing wouldn't it? That infuriated Ben who is behaving like Cain did when his brother Abel had a connection with God that he didn't have...... Murderous Jealousy.