SAN FRANCISCO — At the start of this decade, the Arab Spring blossomed with the help of social media. That is the sort of story the tech industry loves to tell about itself: It is bringing freedom, enlightenment and a better future for all mankind.

Mark Zuckerberg, the Facebook founder, proclaimed that this was exactly why his social network existed. In a 2012 manifesto for investors, he said Facebook was a tool to create “a more honest and transparent dialogue around government.” The result, he said, would be “better solutions to some of the biggest problems of our time.”

Now tech companies are under fire for creating problems instead of solving them. At the top of the list is Russian interference in last year’s presidential election. Social media might have originally promised liberation, but it proved an even more useful tool for stoking anger. The manipulation was so efficient and so lacking in transparency that the companies themselves barely noticed it was happening.

The election is far from the only area of concern. Tech companies have accrued a tremendous amount of power and influence. Amazon determines how people shop, Google how they acquire knowledge, Facebook how they communicate. All of them are making decisions about who gets a digital megaphone and who should be unplugged from the web.