Horace seems to have the same profile as Jacob in "the man behind the curtain." Jacob was mentioned in "Par Avion" by Mikhail Bakunin, who said, "The man who brought me here, who brought all of my people here—He is a magnificent man." Horace brought Ben and his father to the island. Horace is 25-30 years older than Ben at the time of Ben's birth. Therefore, he is about 65-70 at the time we first see Jacob, which seems like it's right for age. He is a mathematician and might have a more important role on the island. He might have had something to do with the Valenzetti equation. Ben closed his eyes when Horace was dead on the bench, a sign of respect and that he considered this man in higher esteem than even his own father. Horace has brown eyes, like the eye in the scene from "The Man behind the Curtain".
Cons: He died on the bench during the gassing. Mikhail was one of the Others, and not part of the DHARMA Initiative, so how he got there should have nothing to do with Horace. Horace died in the purge.
Conclusion: Horace fits the profile, age, and eye color of Jacob. He is responsible for bringing the most powerful man so far (Ben) to the island. Although he 'died' on the bench, there are examples of people who have 'died' on the island before and yet are still alive. In addition, Mikhail could have also been brought to the island by Horace; he could have joined the Hostiles, like Ben. The fact that he wears DHARMA while nobody else does seems to support this, albeit a small amount. Characters on the show aren't random - they are introduced carefully and with purpose.
http://www.lostpedia.com/wiki/Jacob/Theories