Uber, DoorDash and similar firms can’t defy the laws of capitalism after all

IN THE REAL world a flywheel is a mechanical contraption that stores rotational energy. In Silicon Valley it has come to mean something else: a perpetual-motion business that not only runs forever but is self-reinforcing. Thanks to powerful network effects, the theory goes, a digital platform becomes more attractive as it draws in more users, which makes it even more attractive and so on. The end state is a venture that has gathered enough energy to self-levitate and throw off tons of cash.