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 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, , 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.The payout on one of the most richly funded bets of the past decade or so revolves around whether ride-sharing and delivery firms—which once were part of something known as the “sharing economy” but are better described as the “flywheel economy”—can actually ever live up to their heady promise. The outcome will matter to more than just venture capitalists who backed their growth. Whether these flywheels do gather unstoppable momentum is also of interest to regulators worried about technology’s propensity for winner-takes-all business models, not to mention paid-by-the-gig workers caught in its cogs.