Facebook's quarterly earnings were amazing. But Mark Zuckerberg isn't cheering

Facebook just had an incredible past three months for making money, but CEO Mark Zuckerberg's tone isn't that celebratory.

"Our community continues to grow and our business is doing well," Zuckerberg said in a prepared statement. "But none of that matters if our services are used in ways that don't bring people closer together."

"We're serious about preventing abuse on our platforms. We're investing so much in security that it will impact our profitability. Protecting our community is more important than maximizing our profits," the statement.

It's quite a heavy statement from the CEO and cofounder of one of the world's most profitable companies that just achieved another profitable quarter—and saw its stock price reach a new record high.

Facebook brought in $10.3 billion over the last three months, a 47 percent increase from the year prior. It also now has more than 2.07 billion monthly active users. Facebook employs 23,165 people, a 47 percent increase from the year prior.

But Zuckerberg's solemn tone comes as no surprise. For the last two days, U.S. lawmakers have scrutinized Facebook over the Russian propagandists that used its platform to spread politically divisive content during the 2016 election.

“I think you do enormous good, but your power sometimes scares me,” Sen. John Kennedy said Tuesday.

Zuckerberg wasn't present in the hearing. He sent Facebook's General Counsel Colin Stretch who was joined by Twitter's General Counsel Sean Edgett and two different members of the general counsel at Google.

But that doesn't mean the hearing wasn't crucial. Facebook along with Twitter and Google have avoided regulation for the most part from the U.S. government. Now, lawmakers have a bill called the "Honest Ads Act" that would require internet companies to keep a public database of who is paying for political ads. But they're still debating what to require.

"We are not going to go away, gentleman. And this is a very big deal," said Sen. Dianne Feinstein during the hearing with Senate Intelligence Committee on Wednesday. "You have a huge problem on your hands."

Zuckerberg is taking on the challenge. While his prepared remarks read somber, his tone on the beginning of call with investors and analysts Wednesday seemed enthusiastic and confident.

"We're bringing the same intensity to these security issues that we brought to any adversary or challenge that we've faced," Zuckerberg said. “I am dead serious about this.”

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Zuckerberg warned investors that Facebook's profitability may fall in the coming years. Facebook said its expenses may rise by 45 to 60 percent in the next year. For example, Facebook plans to expand its safety and security team from 10,000 to 20,000, General Counsel Stretch told U.S. lawmakers this week.

"It will significantly impact our profitability going forward. I believe it will make our society stronger," Zuckerberg said.

Facebook executives chatted about the company's focus on quality content on the network. While Facebook is known for thumb-stopping puppy videos and other forms of clickbait, Zuckerberg hinted that a ton of time spent doesn't necessarily mean it's valuable.

"Connecting with friends and family and having those meaningful interactions is more important than just consuming content," Zuckerberg said.

That's one reason why Facebook is testing two News Feeds for private content from friends and family and public content from Facebook Pages.

"Not all time spent is created equal," Zuckerberg said. "What we really want to go for is time well-spent."