Why: Amazon's size makes it a target for lawmakers looking to break up big tech, but more specifically its role as both marketplace and vendor has come under scrutiny.
Amazon tries to downplay its size — in his 2018 letter to shareholders, CEO Jeff Bezos insisted the company is still a "small player" in retail, as roughly 90% of shopping still happens offline.
But when it comes to online sales, Amazon is the biggest fish by a considerable margin, taking up 49% of market share. The next biggest player, eBay, commands a little over 6% of the market.
Presidential hopeful Elizabeth Warren has consistently attacked Amazon's business practices concerning small vendors, arguing Amazon can use its masses of retail data to decide when to knock out smaller competitors with its own products.
"When Amazon can tilt the online marketplace in its own favor, small businesses see an immediate impact in their profits," said Warren.
In a rare response, Amazon countered Warren, saying it doesn't use sellers' data to plan its private product launches. "And sellers aren't being 'knocked out' – they're seeing record sales every year," Amazon tweeted.
But it's not just Elizabeth Warren who wants to put Amazon's treatment of sellers under the microscope. European Commissioner for Competition Margrethe Vestager announced in September last year that she was launching a preliminary investigation into Amazon. She said Amazon's use of seller data would be scrutinized.
Who: The Washington Post reported that the FTC will be responsible for Amazon, although it is not immediately clear whether the agency plans to launch any kind of probe.