WhatsApp THE LIST of complaints against the leading web platforms runs long, from privileging their own products and operating both sides of an advertising exchange, to ignoring the problems that result from their activities. Applying conventional rules like antitrust law is difficult, since it is hard to show consumer harm when the service is free. But there is another way to regulate big tech: treat the companies like big banks. The American banking industry learned much from the financial crisis of 2008, the regulatory crackdown and the collapse of return on equity as banks had to build up reserves of capital and liquidity under the new, Dodd-Frank regulations. Today, banks lend to clients and make markets for them, with occasional stresses but no panic. Although many bankers look back longingly at their pre-2008 returns on capital, they still operate lucrative businesses.