I don't know if this has been talked about yet, but I'm just throwing this out. Maybe the reason for why Desmond has been brought back to the island is because Widmore needs Desmond to use the pockets of elctromagnetic energy to somehow destroy the Man in Black. He obviously has something to do with this, due to the fact the negated the energy at the Swan station. I'm sure he is going to be asked to do something dealing with the pockets of elctromagnetic energy, as well as Jin because his name was on the map, so they may need his help in finding these pockets. Maybe they were going to brainwash Jin, so they can have him do what they need. Just a thought. Tell me what you guys think.