Part of me wonders if Thorin had lived, if Balin and the two other dwarves from the original journey that had perished in Moria would have stayed at Erebor. The Lord of the Rings wiki says that Balin was one of Thorin's closest friends. I know that in the film, Balin was with Thorin the day Smaug attacked. I think it likely that Thorin's death would have greatly shaken him and caused him to want to live elsewhere besides the Lonely Mountain, even though he had once wanted to live there and had been kept out for about 100 years. True, it may have had something to do with his wondering about the last ring of the dwarves, but he was there when Gandalf told Thorin that Thorin's father, whom Balin might have known had said Ring, had been captured by the Necromancer, and I think it likely that Balin later learned the the Necromancer was indeed Sauron.