Facebook CEO Mark Zuckerberg arrives to testify in a Senate committee hearing on Capitol Hill. Photo: Chip Somodevilla/Getty Images.

Mark Zuckerberg apologized to lawmakers Tuesday for Facebook's failures in handling user data, but he didn’t waver in defending the company’s business model or its value to society.

Why it matters: Revelations that data firm Cambridge Analytica inappropriately accessed the data of 87 million Facebook users has turned into an all-out crisis for Zuckerberg, who is having to defend his company like never before in Washington. He said Facebook is going through a "broader philosophical shift in how we approach our responsibility as a company."

What we learned:

  • Facebook would "welcome the right regulation" and would work with lawmakers to discuss that, Zuckerberg said.
  • One comment we're sure to hear about again: “I agree that we’re responsible for the content.”
  • Facebook did not tell the Federal Trade Commission, with whom it has a privacy settlement, about the Cambridge Analytica situation when it occurred because it thought the firm had deleted the data, Zuckerberg said. "We considered it a closed case."
  • Facebook may have been subpoenaed by Special Counsel Robert Mueller — he wasn't sure — but Facebook staffers have been interviewed by his team, according to the chief executive.
  • Zuckerberg said it's possible that the data collected by Cambridge Analytica overlapped with the organization that ran the Russian 2016 election interference campaign. "We believe that it is entirely possible that there will be a connection there," he said.
  • Lawmakers said they expected to hold a hearing specifically on Cambridge Analytica.
  • In response to a series of pointed questions from Sen. Kamala Harris, Zuckerberg said he didn't remember being part of any conversation where a decision was made not to tell users about the Cambridge Analytica data gathering.

What they talked about:

  • Cambridge Analytica: Lawmakers pressed Zuckerberg on why the company didn’t tell millions of users they had been effected by the Cambridge Analytica incident or ban the data firm in 2015 when the illicit gathering occurred. He initially said that the company hadn't been an advertiser in 2015, but said after meeting with his staff that in fact they had been later in that year — so they could have been banned.
  • Facebook's power over competitors: Sen. Lindsey Graham pushed Zuckerberg on concerns that Facebook is too large. "You don’t think you have a monopoly," Graham asked. Zuckerberg's response: “It certainly doesn’t feel that way to me."
  • Facebook's broader business model: Many lawmakers asked broader questions about how Facebook gathers user data. To point to his privacy concerns, Democratic Sen. Dick Durbin asked Zuckerberg what hotel he's staying at while in Washington, D.C. Zuckerberg declined to share that information.
  • Facebook's culture: "During the time that it was Facebook’s mantra to Move Fast And Break Things. Do you think some of the misjudgments, perhaps mistakes that you admitted to here, were as a result of that culture or attitude?" asked Republican Sen. John Cornyn.
  • Facebook's politics: Sen. Ted Cruz and others pushed Zuckerberg on whether the company handles content in a way that skews liberal. Zuckerberg pushed back on that idea, including Cruz's suggestion that Facebook might weigh job candidates' political views.
  • Facebook's security: Zuckerberg said that the company’s user data had never been breached although noted that some employee computers had been attacked and seeded with malware in 2013.
  • The platform and discrimination: Zuckerberg said Facebook would be open to letting civil rights groups audit whether its platform is used for discriminatory activities.

Some Republican lawmakers were somewhat supportive of Facebook. Sen. Roger Wicker said he was worried about the prospect of the company being over-regulated, and Sen. Orrin Hatch offered a defense of the social giant's data-driven business model. Zuckerberg responded that "there will always be a version of Facebook that is free.”

How it works: This hearing is a joint session held by the Senate Commerce and Judiciary Committees, with a total of 44 lawmakers participating.

Go deeper: The lawmakers to watch as the hearing goes on

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