When the young boy told MIB that he couldn't kill him (probably Sawyer) because of the rules, MIB began shouting "don't tell me what I can't do" just like John Locke used to.
I think that this is highly out of character for MIB especially because he already made fun of John Locke (sort of) in a conversation with Benjamin Linus about this regular claim.
What do you think? Is this a indication that the real John Locke might still be alive inside of MIB (A)? Is MIB just to some degree infected by John Lockes memories and feelings(B)? Or is it just coincidence (riiiight ;) ), John Locke is dead and the MIB just has something in common with our deceased hero.
I'm looking forward to read your thoughts on this.