Starting with new numbering:
1) Sayid, convinced by Ben that Widmore is responsible for Nadia's death, kills several people at Ben's behest. Then one day Ben just says thanks for playing, I don't need you any more. Sayid, instead of using his "mad ninja skills" to personally go after Widmore without Ben's help, just gets very glum without a boss to tell him who to kill. Then he gives up on the revenge thing and goes off to build houses in the Third World. Some time after the death of "Jeremy Bentham" Ben again approaches Sayid, offering him the chance to kill kill kill. Sayid wants nothing to do with Ben, but whereas Locke's invitation to return to the island and save the island-bound garnered only indifference from Mr. Jarah, Ben's revelation that Hurley's being watched by a Widmore-agent is enough to motivate Sayid to pick up his gun once more. I really didn't think Sayid and Hurley had much to do with one another back on the Island, so I don't see Sayid having some great protective instinct toward Hurley. Is the real reason he accepts the Mission to Help Hurley because Sayid really wants to be set back on the path of fighting Widmore, even though he won't accept Ben's help any more?
2) We know that Sayid felt pissed when Ben gave him the big kiss-off, but is that the only reason he has such a massive distrust for Ben later? In the dock-scene Sayid warns Ben that if Ben approaches him again things will become "extremely unpleasant," i.e., Sayid's ready to kill Ben dead as a Tex Avery roach. That seems a more extreme emotion than he showed when Ben just gave him the air. Did Sayid find out something new about Ben's manipulations? Does he subconsiously suspect that Ben might actually be the one behind the killing of Nadia, but he won't quite let himself consider the possibility that he was so completely fooled?
3) Did Ben have anything to do with the killing of Nadia? It seems unlikely, since in between his turning the donkey wheel and his popping up in Tunisia, the events relating to Nadia's death have already transpired. Mastermind though Ben is, it's hard to see him pulling strings during his ten-month trip to temporal limbo. I suppose that either he or Widmore might have set up the killing long in advance due to foreknowledge given them by time-travel, though Ben doesn't act like he has THAT much foreknowledge. Widmore still seems the more likely candidate, though both of them share the motivation of wanting Sayid back on the Island.
4)Why is Widmore such a pussy during Season 5?
I mean, Widmore in Season 4 is fricking Lex Luthor. He calls together three top specialists to deal with the Island's freakazoid propensities (granted, maybe he calls them together because his past self KNOWS that he WILL call them together). He outfits a freighter with a helicopter and a shitload of C4, plus a shitload of deadly mercenaries. And though the Island's crazy-making radiations seem to keep the freighter's people off in some cases, Widmore's people do end up capturing Ben, killing Alex and doing other dastardly stuff.
But in Season 5, Widmore, knowing that Desmond's brought his daughter back to America, can't do shit to intercept Ben from trying to kill her: Penny's saved only because Ben muffs killing Desmond, who then beats Ben to a pulp before collapsing. Ben also kills Abaddon with complete impunity once Abaddon's helped Locke make his first attempts at O6 enlistement. Maybe it would've been a good idea to send at least TWO men with Locke, Charles W? One would think he could afford another whole squad of mercenaries to keep Locke safe-- though again, maybe Widmore "knows" that Locke's destined to die and (sort of) return to the Island. However, there's no textual support for THAT foreknowledge.
5) What's Miles' role in all this? Faraday performs lots of calculations that help the freighter mission, and he and Charlotte together neutralize the poison-gas weapon so that Ben can't use it as he used it on the Dharmas. But the only reason Naomi gives for Miles being enlisted is that they want Miles to be able to talk to dead bodies on the Island. Once there Miles does this a few times on his own recognizance, but he never explicitly does so looking for particular info that he's been assigned to ferret out. Since dead people aren't much of a resource for helping Widmore's people locate Ben, was there ever a mission-justification for Miles to be on the Island, or is he going to perform a more crucial action in Season 6, one that Widmore knows or suspects he must be there to perform?
It's also interesting that on one occasion Miles does seem to be able to partially read the mind of a living person, as when he declares that "Kevin Johnson" is not Michael's real name. This may have been nothing more than a cutesy throwaway, though. At the very least Miles seems to have far more ability to read dead people.
That's enough for now.
4 hours ago