On March 12, 1989, computer scientist Tim Berners-Lee submitted a simple idea to his colleagues at the European nuclear research lab CERN: to build a networked hypertext system that would manage the institution’s vast hordes of information all in one central place that could be accessed from any computer.

Though he never got the project officially approved, Berners-Lee continued tinkering with it. By 1990 he had finished the first internet browser and the World Wide Web was born.

In a letter released Sunday, exactly 28 years later, Berners-Lee shared that he’s become “increasingly worried” about some of the directions the internet is taking. In particular, he outlined three serious challenges he believes “we must tackle in order for the web to fulfill its true potential as a tool which serves all of humanity.”

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The loss of personal data

First, Berners-Lee warned against the ubiquitous business model of providing free content in exchange for personal data, like a birthday and email address, which millions of users hand over with little hesitation.

“As our data is then held in proprietary silos, out of sight to us, we lose out on the benefits we could realise if we had direct control over this data, and chose when and with whom to share it,” he said, adding that dizzyingly long Terms & Conditions documents don’t help the situation.

The debate about how best to protect personal information online is robust among technologists, who gathered in at a San Francisco summit in January to brainstorm new standards around digital privacy.

In his anniversary letter, Berners-Lee specifically warned of repressive regimes who collaborate with or coerce tech companies to use widespread data collection against their own citizens.

“Even in countries where we believe governments have citizens’ best interests at heart, watching everyone, all the time is simply going too far,” he writes.

Fake news: The “wildfire”

Berners-Lee added his voice to the chorus of people gravely concerned about the explosion of fake news, or deliberate misinformation designed to appeal to readers’ biases and make money through viral clicks.

“Through the use of data science and armies of bots, those with bad intentions can game the system to spread misinformation for financial or political gain,” Berners-Lee said.

In December, Facebook announced new steps to curb fake news on its platform after months of continuous criticism. The plan included new tools to make it easier for Facebook users to flag fake stories and a collaboration with the respected journalism organization the Poynter Institute to independently investigate claims. But Berners-Lee says internet giants need to do more.

“We must push back against misinformation by encouraging gatekeepers such as Google and Facebook to continue their efforts to combat the problem, while avoiding the creation of any central bodies to decide what is ‘true’ or not,” Berners-Lee said.

The problem of political advertising

In his final warning, Berners-Lee pointed out that online political advertising has perhaps become too targeted and sophisticated for its own good. He cited one academic source claiming as many as 50,000 variations of campaign ads were served every day on Facebook during the 2016 presidential election, though targeted advertising is notoriously hard to quantify.

“Targeted advertising allows a campaign to say completely different, possibly conflicting things to different groups,” he noted. “Is that democratic?”

Such online electioneering exploits a “blind spot” in campaign regulation, he said.

In internet history, Berners-Lee is notable because he never charged money for the web technology he invented or patented his contributions. He now leads the World Wide Web Foundation, a nonprofit organization with a mission to “advance the open Web as a public good and a basic right.”

“It has taken all of us to build the web we have, and now it is up to all of us to build the web we want – for everyone,” he said.