Or Jacob is merely the previous Christian. The island uses some form to communicate with people, and for Ben it was Jacob. Perhaps once Ben is no longer the chosen one, the manifestation for the island has changed as well.
It appears that we are seeing two versions of time/space travel. One is what we've seen with Desmond, as well as the rat in Faraday's early experiment. Desmond's physical being didn't travel through time, only his consciousness, either forward or backward.
But we know that with Ben and his latest jump off the island, he moved through space physically as well. Hmmmm, interesting. I'm certainly looking forward to where this all goes.
I did have one complaint last night. What's with the whining about having to lie? Obviously they had to lie...they certainly couldn't tell the world that they'd been on a mystical island that just disappeared. Even if Widmere wasn't looking to use them to get to the island, they certainly couldn't tell the truth about where they'd been, and you'd think that would have been pretty obvious the first time the smoke monster did it's dance.
But otherwise, it was a very solid finale, with lots of good answers and lots of good questions.
It's going to be interesting to see the structure of the show next year - they switched this year from flashbacks to predominately flash forwards, but now we've caught up to the point real time with them off the island. Doing the flashbacks and forewards might be tough now structurally, since some characters are off island and some on in current time. I'll be very interested to see how they reinvent things.