A theory about the first episode of this season: I think that Jacob, just like his Nemesis/the Monster, has the ability to take over dead bodies. I think the reason that Sayid has "come back to life" is that Jacob is now controlling his body. I know that Jacob's supposedly dead, but why else would Jacob put so much interest into Hurley bringing Sayid to the Temple and telling the Others that if Sayid died, they wre pretty much screwed? I don't think it was Sayid dying that would put the Others in danger, it was Sayid not being able to get to the Temple so Jacob could assume his dead body. What do you think? It may be a little out there, but I think Jacob giving Hurley the guitar case was just covering his steps in case he ever died.