Big tech's giant power could be challenged in blockbuster antitrust probes - here's what that means for Apple, Amazon, Facebook, and Google

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.

Why: Although details about what a Facebook antitrust investigation might look like are thin, it would not be a big leap to assume that regulators may choose to inspect its ownership of Instagram and WhatsApp.

Calls for Facebook to be broken up have grown in volume after a series of disastrous missteps, including election interference on the social network in 2016 and the giant Cambridge Analytica data breach last year.

Leading those calls have been former Zuckerberg allies, like early investor Roger McNamee, and more recently, Facebook cofounder Chris Hughes. In a New York Times op-ed, Hughes said Facebook, Instagram, and WhatsApp should be divided into three publicly traded companies.

"The American government needs to do two things: break up Facebook's monopoly and regulate the company to make it more accountable to the American people," he added. Facebook CEO Mark Zuckerberg said the proposal "isn't going to do anything to help."

Facebook has already been clobbered with one antitrust ruling this year. Germany's antitrust regulator told the firm it must stop forcing users to allow it to collect and combine their data from sources outside Facebook, like Instagram and WhatsApp.

Who: Reuters was among those to report that it would be the Federal Trade Commission that would oversee a Facebook antitrust investigation. The FTC is currently drawing to a close a probe into the Cambridge Analytica breach, which could result in a fine of up to $5 billion for Facebook.

Why: Google's sheer ubiquitousness as the world's most popular search engine, which hoovers up reams of data about its users, as well as providing the mobile operating system for the vast majority of non-Apple smartphones (while also selling its own smartphone the Pixel) could be sources of concern for lawmakers.

In Europe, the company has already been hit with three antitrust fines over the past three years. The European Commission has fined Google:

• $2.7 billion in 2017 for promoting its own shopping service above competitors.
• A record $5 billion in 2018 for abusing the dominance of its Android operating system.
• $1.7 billion in 2019 over its AdSense advertising service.

Google is currently appealing the first two fines, but the Android ruling has already resulted in change, with Google announcing it would make it easier for Android users to select competing browsers and search apps.

Who: The Wall Street Journal reported that the DOJ is gearing up to launch an antitrust investigation into Google. The scope of the investigation is unclear, but a Washington insider source told Business Insider that it's likely to examine everything including Adtech, privacy, and Google search.