House lawmakers, who had opened an investigation into the tech companies in June 2019, made the most of it. Representative Jerry Nadler, Democrat of New York, confronted Mr. Zuckerberg with the C.E.O.’s own emails, saying they showed a plot to take out a young competitor. Representative Jim Jordan, Republican of Ohio, said Google was biased and asked Mr. Pichai whether the company would change its products to help elect Joseph R. Biden for president.
In one of the sharpest exchanges, Representative Pramila Jayapal, a Washington Democrat, confronted Mr. Bezos on accusations that an Amazon lawyer had lied to the committee about how the company develops its own products. She asked him to answer whether it misused data with a yes or no.
“I can’t answer that question yes or no,” said Mr. Bezos, appearing rattled.
Yet while the hearing was ripe with theater, any impact will be limited by antitrust laws that were created a century ago and that are imperfect for corralling internet firms. Since the 1980s, enforcement officials have used the notion of consumer welfare as the predominant test for antitrust violations — generally meaning that if prices are not going up, the markets are most likely competitive enough. The tech giants have generally not driven up prices of digital services or consumer goods; many do not charge at all for services like Google Maps or Instagram.
While Democrats at the hearing indicated they were more inclined to change antitrust law, Representative Jim Sensenbrenner, Republican of Wisconsin, said he did not think the laws needed to change. Ultimately, Congress doesn’t have the power to break up the companies.
Still, the proceedings provided fuel to other investigations of the tech companies by the Justice Department, the Federal Trade Commission and state attorneys general. The Justice Department is expected to soon announce charges against Google accusing it of abusing its dominance in online advertising, people with knowledge of the investigation have said. The F.T.C. is preparing to question Mr. Zuckerberg under oath in its investigation of Facebook’s grip over social networking and acquisitions of nascent rivals.
“This is a critical juncture in how the Washington policy clash with the titans of Silicon Valley unfolds,” said Gene Kimmelman, a former Justice Department antitrust official and a special adviser to the consumer advocacy group Public Knowledge.
Regulators around the world are also moving to limit the power of the tech giants. Europe has led the charge with antitrust investigations and Margrethe Vestager, the region’s top trustbuster, recently vowed to take a harder line on the companies. On Wednesday, Turkey passed legislation giving its government sweeping new powers to regulate social media content.