The Department of Justice said on July 23 that was launching a broad investigation into market-leading online platforms in search, social media, and e-commerce to determine whether such firms are hampering competition. While it did not specifically name the companies it's investigating, the DOJ made its announcement after a report from The Wall Street Journal indicated that the DOJ and Federal Trade Commission had split jurisdiction over probing Amazon, Facebook, Google, and Apple. Shares for Amazon, Apple, Google parent Alphabet, and Facebook were tumbling in after hours trading on July 23, wiping away $33 billion between the four companies. Amazon was down 1% following the news on July 23, a $9.8 billion hit to its market capitalization. Read more: Amazon reportedly has an ambitious plan to change the way we grocery shop — here's what we know about it so far Executives from these companies testified before a Congressional antitrust subcommittee in July to answer questions about their business practices and whether they make it more difficult for smaller companies to compete. Democratic senator and 2020 presidential candidate Elizabeth Warren called for regulation of big tech firms like Amazon earlier this year. Under her plan, large firms with annual global revenue of $25 billion or more would be classified as platform utilities, and certain past acquisitions could even be reversed. The scrutiny has prompted tech firms to defend their business practices more vocally than ever. In his annual letter to shareholders in April, Bezos didn't directly address the discussion around tech regulation. But he did stress the success that small and medium sized companies have had on his platform and referred to Amazon has a small player in the worldwide retail space. Bezos liquidates $1 billion worth of Amazon stock per year to fund Blue Origin, he said when speaking at an event hosted by Business Insider parent company Axel Springer last April. The only way I can see to deploy this much financial resource is by converting my Amazon winnings into space travel, Bezos said at the time. Blue Origin is expensive enough to be able to use that fortune. Bezos may not be as much of a philanthropist as other tech giants like Bill Gates. But he does operate a charity called the Bezos Day One Fund, which funds non-profits that help homeless families and builds preschools in low-income communities. He started the fund with $2 billion, so it's possible that he may be putting some of the cash from the sale toward that project.