When Mark Zuckerberg started Facebook in his Harvard dorm room, Chris Hughes was one of his roommates and became a Facebook cofounder. Hughes left Facebook more than 10 years ago, but his time at Facebook earned him a fortune in the hundreds of millions of dollars.

Now Hughes says that Facebook has grown too big and powerful. In a lengthy opinion piece for the New York Times, he argues that the company gives too much power to founder Mark Zuckerberg.

"Mark is a good, kind person," Hughes writes. "But I’m angry that his focus on growth led him to sacrifice security and civility for clicks.

"I’m disappointed in myself and the early Facebook team for not thinking more about how the News Feed algorithm could change our culture, influence elections and empower nationalist leaders. And I’m worried that Mark has surrounded himself with a team that reinforces his beliefs instead of challenging them."

Hughes argues that an expected $5 billion fine from the Federal Trade Commission won't be sufficient to hold the company accountable. He calls for bigger regulatory moves—including breaking up the company.

"The FTC’s biggest mistake was to allow Facebook to acquire Instagram and WhatsApp," Hughes writes. "The Instagram acquisition guaranteed Facebook would preserve its dominance in photo networking, and WhatsApp gave it a new entry into mobile real-time messaging."

Reversing a merger after it happens is more difficult than blocking it beforehand, but Hughes argues that it can be done. He points out that federal regulators forced Whole Foods to spin off a recently acquired competitor, Wild Oats, in 2009.

Hughes also calls for a new agency in charge of regulating technology companies, with a focus on privacy. He argues that this agency should also "create guidelines for acceptable speech on social media."