Amazon.com Inc.'s vaunted e-commerce empire has taken some lumps during the Covid-19 pandemic, with delays and out-of-stock challenges sending some customers to rivals like Target Corp. and Walmart Inc. The Washington Post reports on the challenges facing Seattle-based Amazon (NASADQ: AMZN), whose share of the U.S. e-commerce market fell from 42.1% in January to 34.2% in April, according to market researcher Rakuten Intelligence.