remeber one thing about Hagen; he had advised the Don that they should get into the heroin business because if they did not do so at that point, the other families would eventually (5 or ten years down the line) they (the other families) would be have amassed a lot of money and would be able to buy more politicians, more protection and come after the Corleones. In the novel, I remember the Don thinking something in his head about Hagen (or Sollozo??) when Hagen suggested the move into the drug business.