Tonight's LOST
If they neutralize the electromagnetic force in 1977, then it won't be able to go off in 2004, so they'll never crash on the island and never have to return to the island because (to them) there's nothing to return to. Thus, they will never have neutralized the force and it'll still go off to crash their plane. Which is the problem that I believe Daniel may have tried to explain away, though I'm not sure. He tends to mumble.
BUT. What if there is such thing as destiny? What is, no matter what they mess with in 1977, they will still return to the island in 1977? I kind of think it would be awesome if they manage to neutralize it in 1977 and then the whole show just reverts to them on the plane landing in LA. Then they could spend next season showing us how they got to the island anyway, just with different configurations? Though I feel like that would be really risky - that might make a lot of fans angry enough to not come back next year. What can I say? I like risk.
Also...I totally called that Widmore is Daniel's father. I mean, I'm sure half the country did also, but I'm just saying. I called it.
And finally.... Really? They really fucking killed Daniel? That makes me quite sad. Also pissed.