“Think of the flow of friends through Facebook, the flow of renters through Airbnb, the flow of opinions through Twitter, the flow of e-commerce through Amazon, Tencent, and Alibaba, the flow of crowdfunding through Kickstarter, Indiegogo, and GoFundMe, the flow of ideas and instant messages through WhatsApp and WeChat, the flow of peer-to-peer payments and credit through PayPal and Venmo, the flow”