I have a theory that I don't feel like blowing up into a massive thought process, but A Christmas Carol made me think of the whole "what could've happened" motif that the show has been pushing on us since they crashed in the beginning. It's so very obvious to us as viewers that every member of the cast really had nothing but bad things waiting for them if the plane had landed in LA. And as the show has gone on each of the cast has figured that out on their own starting with the un-paralyzed John Locke until most recently Jack. Everybody has come to realize that however terrible the encounters on the island have been, their lives are all considerably better than had they landed and led their lives without the crash. Jacob's encounter with each of them, I believe, is the defining point in that person's life that brought them to the island.
If you look back at the encounters, YES he touches all of them but the most important thing is the event taking place. I think every one of those scenes were THE defining moments in each of their lives that A) brought them to the island and B) Allowed each of them to accept the life they were given.
Jack is in the room with vending machines about to explode over it not working, as well as his father's behavior, but Jacob provides a sense of calmness and acceptance that I think Jack hadn't known before then, and it's that encounter that allows him to accept his life on the island.
Kate is shoplifting in the store and Jacob all but encourages her rebellious criminal lifestyle, which ultimately brings her to the island.
Sawyer is told not to write the letter by his uncle, but when his pen runs out of ink, Jacob encourages him to continue by giving him a new pen, which ultimately leads to his vengeful spirit, leading to his con-artist lifestyle, and lands him on the plane, bringing him to the island.
Hurley's encounter is obviously Jacob flat out telling him to get on the plane, so there's no need to explain anything further, except still wondering what's inside the guitar case. Whatever it is, it brought Hurley to the island. Maybe something to do with Charlie we still haven't seen.
When Jacob goes to Sun and Jin's wedding, it isn't so much that he's bringing them to the island, but telling them to never take their love for granted. THIS is the event that more or less brings Sun back to the island.
Then there's John Locke's encounter with him that is the most obvious and give's him the faith to keep going, until he get's to the island with a brand new lease on life. Another important part of that scene, is the fact that Jacob "apologizes for what happens to him." I think he's talking about what happens to him eventually with the man in black, being used as a pawn, and his death.
Finally, the encounter with Iliana is basically the first meeting between the two and I think he explains everything to her and the help that is needed from her, ultimately bringing her to the island.
So basically, while most people are saying that "Jacob touched each of them" or "Jacob gave each of them something" I think the real focus should be on that fact that Jacob's goal is to prove to the man in black that humanity is worth saving. And he intends to do this by "having a more distant role, by helping or nudging things along without controlling events." If you look it up, that's one of the things Taweret is believed to do.
Thanks for reading guys, let me know what you think.