Chris Dixon on the "second-order effects" behind a16z's early bets on Oculus, drones, and crypto: "I joined the firm in 2013. I talked to Marc and Ben, and I said, 'Hey, I wanna do this crazy stuff,' and they were like, 'Great.'" "That led to a couple of themes at the time, and they're all kind of what I would call kinda second-order effects. You had smartphones obviously start in 2007, and by 2013 had gotten mainstream, and there were all these kind of first-order effects like building apps…