In this articleBTC.CB=COINThe logo for Coinbase Global Inc, the biggest U.S. cryptocurrency exchange, is displayed on the Nasdaq MarketSite jumbotron and others at Times Square in New York, U.S., April 14, 2021.Shannon Stapleton | ReutersCoinbase shares are down more than 20% in pre-market trading Monday.Coinbase makes a commission when people buy and sell cryptocurrencies. Monday's