David Booth on the wheels of social capital, and how one cosign behind a cold DM compounds into hires, deals, and entire companies: "The most important skill in this town, or in this industry, or perhaps in the world, is your ability to identify things before the market." "If you're an investor, it's companies. If you're a hiring manager or a founder, it's people. Sometimes it's products." "There's no way of recording that. There's no hipster leaderboard that says, 'This person found this…