Sen. Elizabeth Warren introduced a crowd-pleasing proposal Friday in her bid for the Democratic presidential nomination: Break up the biggest technology companies, including Amazon, Facebook and Google.

In a blog post, the senator from Massachusetts promised “big, structural changes” to the tech sector, including undoing some of the mergers that have enriched the tech giants. The policy would also prevent those companies from using their service to sell other goods and services that they own.

Her proposal marks one of the most aggressive bids to rein in near-trillion dollar corporations in the tech sector.

The tech giants were largely quiet Friday, but others around Silicon Valley were unimpressed.

“Warren is jumping on the bandwagon of blaming tech for all societal ills,” Bilal Zuberi, a partner at Lux Capital, which has headquarters in New York and Menlo Park, said in an email.

“She doesn’t understand. If you do this and China doesn’t break up Alibaba, you can kiss American tech leadership goodbye,” tweeted Zach Tratar, a software engineer.

Warren’s plan would put particular strictures on tech companies that have more than $25 billion in revenue and operate a public marketplace or exchange (what Warren calls “platform utilities”).

Google would be forced to split off its ad and search businesses. Warren also called for tech giants to stop transferring or sharing data with third parties.

And “Amazon would not be able to sell its own versions of popular items on the Amazon Marketplace,” she wrote in the blog post.

The biggest of the big The proposal from Sen. Elizabeth Warren, D-Mass., to regulate big tech companies would fall overwhelmingly on the Bay Area’s internet and hardware giants. Bay Area companies with revenue of more than $25 billion Annual revenue Apple, Cupertino $261.6 billion McKesson, San Francisco $213.5 billion Chevron, San Ramon $158.9 billion Alphabet, Mountain View $136.8 billion Wells Fargo, San Francisco $101.1 billion Intel, Santa Clara $70.9 billion HP Inc., Palo Alto $58.7 billion Facebook, Menlo Park $55.8 billion Cisco, San Jose $50.8 billion Oracle, Redwood City $39.8 billion Hewlett Packard Enterprise, San Jose $30.7 billion Source: Bloomberg

Read More

Representatives from Amazon, Facebook and Google did not immediately respond to requests for comment.

The tech sector has come under fire in recent years for controversies related to data privacy and misinformation. Critics say it’s time for more government supervision.

“Warren’s proposal to break up big tech is what Silicon Valley needs,” David Heinemeier Hansson, the Malibu-based creator of the Ruby on Rails programming language, said in a tweet Friday.

“They’ll kick, scream, lobby. And then 10 years after it’s done, they’ll all laud its vision, as they count the proceeds from the next round of progress it’ll enable,” he added.

David Ryan Polgar, a tech ethicist in New York, said Warren’s pitch was unsurprising.

“I think a larger issue that is here is, big tech has unchecked and unelected power, and that power also massively influences how we see the world, how we get our information and how we connect,” he said.

Breaking down big tech companies is one possible solution, he said, though “realistically, I don’t think it’s going to happen in the next year or two.”

Some members of the Bay Area tech community said the proposal showed how little Warren understands the industry.

“If you think some intervention is needed against some industry or company, you need to define what exactly the harm you’re addressing is ... and how the specific remedy you propose changes that,” Benedict Evans, a partner at Menlo Park venture firm Andreessen Horowitz, tweeted. “‘Break it up’ is not a policy analysis.”

“There is no doubt that misfires happen,” said Zuberi of Lux Capital. “But only someone without doing any economic impact analysis would come up with a random target to break up companies doing more than $25 billion in revenues.”

In her blog post, Warren criticized tech giants for using their enormous wealth to snap up smaller competitors and stamp out innovation. She said venture capitalists are now “hesitant to fund new startups.”

Bradley Leimer, whose consulting firm, Unconventional Ventures, matches startup founders with funders, said Warren isn’t wrong.

“Services are making money by harvesting our data and doing it in more discreet ways, but ... the next iteration of those platforms aren’t able to see the light of day,” he said. “They are taken from where they could go by being acquired early by these large institutions.”

Warren appears to be trying to set herself apart with the proposal for harsh regulation. But some of her rivals, including Sen. Bernie Sanders, D-Vermont, and Sen. Amy Klobuchar, D-Minn., have also taken swings at big tech.

“A lot of people in the industry realize change is coming,” Polgar said.

Melia Russell is a San Francisco Chronicle staff writer. Email: melia.russell@sfchronicle.com Twitter: @meliarobin