I'm kind of surprised that this has not been brought up yet, but for myself, it was one of the first questions I asked to myself when I heard of Steve Jobs' death. Given the nature of his health problems with his pancreatic cancer and then his liver transplant I wonder if his dietary lifestyle contributed to his early death.
I had a relative who developed dementia and Alzheimer's at a very early age, he was a very active and extreme vegan. His doctor told him--believe it or not--that he wasn't eating enough fat, but as far as I know he continued to eat this way and his wife continued to prepare vegan food for him in his last days. He was in his mid-60's when he passed.
I don't think you need tons of animal products to live a long and healthy life, but I certainly do think if you are a vegan or vegetarian that, liver, eggs, and dairy are invaluable for sustaining health.
Comment: I think it's unfortunate the Jobs' passed. However, this is something important to discuss, maybe it's too close to home, I'm not sure. People tend to have some pretty hard and fast opinions when we aren't discussing particular examples and citing studies of groups of "nameless" people. But when we bring in a real world example all of the sudden those opinions fall to the wayside and we no longer know anything anymore?