By the time of the hearing's first break, Facebook's share price had risen by 5% - adding £3bn to his net worth.
Facebook believes approximately 87 million people were compromised in the scandal; however, the application that Cambridge Analytica used was created in 2014 and has been collecting information from Facebook users for several years, in addition to information from other apps.
They asked the company's CEO about how much data Facebook collects on people when they aren't logged into the service-or when they don't even have an account.
Facebook CEO Mark Zuckerberg acknowledged Wednesday that regulation of social media companies is "inevitable" and disclosed that his own personal information has been compromised by malicious outsiders.
With news about Facebook and its data sharing and selling practices in hyperfocus this week, it's important to know if the platform is using your data. Mr. Zuckerberg also stated he would be open to possible regulation of how companies like his handle users' data. I don't think that's hard for you to say yes to unless I'm missing something.
Patience with the social network had already worn thin among users, advertisers and investors after the company said last year that Russian Federation used Facebook for years to try to sway USA politics, an allegation Moscow denies.
But he stiffly defended Facebook's use of the data and postings of the 2.2 billion users of its free platform - in order to attract the ad revenue that the $480 billion company depends on. "I started Facebook, I run it, and I'm responsible for what happens here", he said.
Facebook had not taken a broad enough view of its responsibility for people's public information, said Zuckerberg. "If you're logged into Facebook and visit a website with the Like button, your browser sends us information about your visit", Facebook's website says.
Zuckerberg acknowledges that the Facebook user agreement is problematic..
Representative Eshoo, following up on her question about Zuckerberg's personal data, asked if he is "willing to change your business model in the interest of protecting individual privacy?"
"This is a wake-up call to Silicon Valley and the tech community that if you let these things get out of hand, having grown up in a very lightly regulated environment, you could end up with a lot more regulation than you seek", he said after the hearing.