On the heels of WSJ's D.Live 2018 tech conference in Laguna Beach, Calif., Personal Tech columnist David Pierce highlights a few of the most interesting moments, from Gwyneth Paltrow's Goop startup secrets to the director of Google's threat analysis group discussing countries using the internet as a battleground. Plus, tech columnist Christopher Mims talks with Rodin Lyasoff, CEO of the Airbus research group A3, about the future of flying cars.