Mariana Minerals CEO and former Tesla Senior Manager @tbc415: vertically integrating for the sake of vertically integrating doesn't make any sense. Every vertical integration decision needs to boil down to one question, especially early on: does the company exist or not if you don't make the decision to vertically integrate? "That makes a decision easy." "That could be a number of drivers—the part doesn't exist, the technology doesn't exist, or the cost is so insanely high that the company…