"Ben unwillingly divulges information to Locke about the island, taking him on a journey to various locations including strange monuments and the mysterious Jacob. Back at the beach, Juliet's secret is revealed. Flashbacks will show us the origins of DHARMA and the history of the island, including 'the purge'."

Nestor Carbonell (Richard Alpert), Marsha Thomason (Naomi), Tania Raymonde (Alex), Mira Furlan (Danielle Rousseau), Francois Chau (Dr. Marvin Candle), Madeline Carroll (Annie), Samantha Mathis (Olivia), Doug Hutchison (Horace), Carrie Preston (Emily), Jon Gries (Roger Linus), Sterling Beaumon (Young Ben), Andrew Divoff (Mikhail), M.C. Gainey (Tom)

From that clip, it looks supiciously like Jacob is an alter-ego of Ben's

Episode 3.20: The Man Behind the Curtain (Ben-centric)
Airdate: May 9, 2007

* 05/04 - We will learn more about Jacob next week. Source: Lost Podcasts
* 04/25 -
* 04/23 - Ben begrudgingly begins to introduce Locke to the secrets of the island, beginning with the mysterious Jacob. Meanwhile, Juliet's secret goes public. Guest starring are M.C. Gainey as Mr. Friendly/Tom, Tania Raymonde as Alex, Andrew Divoff as Mikhail, Nestor Carbonell as Richard Alpert, Marsha Thomason as Naomi, Sterling Beaumon as young Ben, Jon Gries as Roger Linus, Carrie Preston as Emily, Doug Hutchison as Horace, Samantha Mathis as Olivia and Madeline Carroll as Annie. Source: ABC
* 04/23 - Lost Spoilers offers us a summary of the spoilers Cuse and Lindelof revealed in the latest podcast: Ben has been in love. We will get a "sense" of it in 2 weeks. Source: Lost Podcasts
* 04/17 - Lost Spoilers offers us a summary of the spoilers Cuse and Lindelof revealed in the latest podcast: We will see Dharma before the purge and we might see how they repelled the smoke monster with the sonic fence. Source: Lost Podcasts
* 04/17 - I hear we're going to meet Ben's mommy and daddy. We will get much more info about Ben's origins and the origins of the island. Source: Kristin on E!Online
* 04/16 -
* 04/06 - Lost Spoilers offers us a summary of the spoilers Cuse and Lindelof revealed in the latest podcast: More info on the DeDroots soon. Source: Lost Podcasts
* 03/27 - It looks like you'll get more action on Hurley's... van. Producers are currently casting for a "Roger," a working-class janitor in his early forties who is bitter about his place in life but has higher aspirations. The notice says of the character, "He has troubled and complex relationship with his son; he finds himself caught up in a mysterious situation beyond his imaginings; and the actor must not be claustrophobic." Pretty sure this is the skeleton — "Roger Work Man"—from Hurley's episode. Source: Kristin on E!Online
* 03/27 - Lost Spoilers offers us a summary of the spoilers Cuse and Lindelof revealed in the latest podcast: We'll see the Dharma van again, it will have a flashback of sorts and see how it came to be in the jungle. We will also see another Volkswagen product on the island. Source: Lost Podcasts
* 03/23 - Looks like episode #320 is 'hippie-centric' with a flashback to the '70's. Features Horace, a scientist/mathematician and Olivia an attractive elementary school teacher. Both embody a 'hippie' idealism. Olivia may show up later in other episodes. Source: secretagentman @ TWoP

I had such a crush on her when I was younger due to Pump Up the Volume and Super Mario Bros.

Zombie Dad

You are.

Jacob is their "savior" who has not yet returned to his flock (the Others). They follow his teachings and wait for his return to usher in a new era. This jives with John's reception at Other's camp. They thought it was their savior returning to them.

Also, think about the Jesus parallel. Before finding himself, he had to spend time in the desert tempted by Satan. He had to pass the test before taking the next step. Same with John and his father.