so, ok, how about ...this:
the smoke monsters is the devil guy. he's spooky, makes a weird accounting machine noise, and likes to drag people to their death. he has the ability to manifest himself as other people, as long as their bodies are on the island (jack's dad, ecko's brother, horace, etc).
his goal the whole time is to find a loophole to kill his brother (?) jacob, which for whatever reason he can't do himself. so, in smoke form, he has "scanned" others on the island looking for a way to do so. he scanned ecko, saw that this was a truly apologetic, repentant christian guy, and just flat out killed him. he saw / scanned locke, recognized that it was a guy who could be manipulated (by his father, by ben, etc), and saved that note for later. he scanned ben, saw that ben was an evil, squirrely kinda guy (with giant bug eyes) and found in him a murderer. he manifested as ben's daughter alex (also on the island) and told ben to listen to whatever "john locke" said.
every time we saw "jacob" in the cabin, we actually saw the devil guy. sometimes, he was already manifested as christian -- the same form that convinced locke to leave the island and be killed. and we saw the "note" from the actual jacob on the wall of the cabin last week, indicating jacob had left to lie "in the shadow of the statue".
locke's body returns, smokey takes over. smokey manifests as alex, telling ben to listen to locke. locke tells ben to kill jacob. loophole found.
the others are the good guys, and have always been (they keep saying it!). ben may have been a shit, but the rest are good. at some point, the "tribes" fragmented, with ben's group being lead by a false jacob (devil guy), and the others (like elan) knowing the true whereabouts of jacob. richard may have been the cause of this, when he left the island to look for locke. together, the others are the disciples, and richard alpert's job is to continually (jack) sheppard them. jacob brought alpert to the island via the black rock to fill this role.
their language is latin, as evidenced by juliet - and later alpert, when he respond's to elan's question about who lives in the shadow of the statue; "he (jacob) who will save us all."
on the beach, the devil guy tells jacob that "it always ends the same" -- a potential reference to time (travel) looping over and over, where the outcome is always the same. jacob responds that it "only ends once; everything else is progress" -- potentially meaning that they make slight advancements to finding a way for peace every time, before "hitting the reset". he visits the characters in their past, setting them on their paths -- moving the pieces of the "chess game."
daniel's theory was correct; little changes don't impact time, but large ones could. however, his "blow up the island" theory wasn't big enough. killing a god, however, could be.
enter next season where basically the same situations will happen, only perhaps taking slightly different paths on the way to achieving peace -- a montage of everything that happened in the previous 5, but with different (better?) results. and perhaps the only way any of this would have ever come about is by jacob recognizing he had to be killed to inspire it. their plane still crashes on the island, and jack wakes up in the forest. as shown in the split-second preview for next season.
