The touch
Did you notice the tapestry that Jacob was weaving showed a pyramid effect with one figure at the top feeding down to more and more figures below? I think this is quite relevant as it could explain why Jacob touched some of the survivors. I think once you have been touched and touch someone else you pass something on (could it be the mysterious virus people were immunising against).
There seems to be 2 sides in the show so far, those who believe that what happens, happens and those who believe they can change the future. I think you become a variable once touched by Jacob. Lets say time and destiny are pre-determined paths and if you went back in time and did something that should re-shape the future, course correction would occur to bring things back on track, however, if you have had ‘the touch’ you are no longer bound to your pre-destined path allowing you to become a variable. Daniel Fariday was not touched by Jacob and therefore Ellie had to follow the correct course and send Daniel back to be shot by herself.
What do you think?

I think there is a good possibility you are right. With the bomb going off, there must be focus on what it is possible to change in the past and this idea gives a framework for that.
Well, it remains to be seen, I guess, if the events of the season finale represent change or just whatever happened. I think it’s much more likely that it’s just what happened. I wrote a whole theory about it a few days ago. The bottom line is that the incident, as it was going, was moving towards certain disaster until the Losties got involved. In fact, without their involvement the Swan Station and the numbers protocol would have been completely impossible… so I was leaning heavily towards WHH before and not I’m absolutely positive of it. They changed nothing.
So all of those people who were in the past that Jacob touched were unable to make any changes so I think it means something else.
arterymedia, I certainly like the idea, that perhaps the ‘touch’ of Jacob may have made them variables.
I do think there is much more to this, as well.
We will not know until Season 6 what may have changed, and if it changed things for the better or for the worse. Understanding this, may provide further insight into Jacob’s true nature.
However, we do know that ‘the losties’ presence in the past, is representative of change, either way, whatever the outcome.
Nah, sorry guys, but I actually don’t think so. First of all, Juliet was the only one durinf the incident who didn’t meet Jacob, it would then make little sense that she would set it off(If she really did, we saw a flash, not a big boom) But more importantly, we all know about Sayids failed attempt on young Benjamin – whose fate at least seems so far as a perfect product of course correction. Also, we only have Daniel’s word on themselves being variables, yet he gives no explaination how he came to this conclusion. He did acknowledge Desmond as a variable – which, by Daniel’s own words made Dessie special. And then one day, he just like: Hey, what the Hell, let’s all be special, let’s change history(Ironically soon thereafter Telling young Charlotte exactly what he tried not to – thus, going against his own theory even more so)