This week some lawmakers called for a privacy bill of rights.
The Facebook finder and CEO owns more than 401.4 million shares in his company, and following the rise in stock prices, his stake is now worth $66bn (£46.2bn).
"I think we're not any closer to regulation of Facebook, but I do think Congress put Facebook on notice, basically saying Facebook has to clean up its act or we will come in and do it for you".
"How can consumers have control over their data when Facebook does not have control over the data?" asked Congressman Frank Pallone of New Jersey at the beginning of the hearing.
Seemingly unimpressed, Republican Senator John Thune of South Dakota said Zuckerberg's company had a 14-year history of apologising for "ill-advised decisions" related to user privacy. But he said his company "can do a better job of explaining how advertising works".
Yet, when asked if his data had been improperly used, he replied: "Yes".
Back in 2011 and 2012, while the Lewiston native was working as an operations manager for Facebook, he warned his supervisors that the company was not doing enough to protect the data of its users. "That goes for data on users that click on your profile, how much time they spend on it, and what parts they mostly explore".More news: Uttar Pradesh CM, Yogi Adityanath, speaks on Unnao rape case
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"Data is the new oil", Kelly said.
She didn't download the personality quiz app; one of her friends did. "A lot of Americans are waking up to the fact that Facebook is becoming sort of a self-regulated superstructure for political discourse", he said. That will cover the pictures from my high school graduation and my first semester in college as well as the memories of my first year in NY. Seventeen percent deleted their Facebook app from their phone, 11% deleted from other devices, and 9% deleted their account altogether.
Nor is Facebook apparently expecting new legislation that could hurt its bottom line.
"We have kicked off an investigation of every app that had access to a large amount of people's data before we locked down the platform in 2014. What information have I innocently shared has become used in a way I'm absolutely uncomfortable with?"
I get that you don't knowingly sell my data, and just use it primarily to help relevant advertisers target me. Some people have demanded to know.
"What would you do if you knew the friend, unfriend him or her?" she said. "Some of the questions asked of Mark Zuckerberg didn't suggest to me a level of understanding of the nuance of privacy by some of the senators".
Kita Bryant, 36, a photographer from Atlanta who runs the website It's Really Kita, says she feels like she dodged a bullet.
The number of users affected by the Cambridge Analytica breach by state. "I wasn't as anxious as everyone else, but I am glad that I didn't have to worry about my personal info getting out there".
For all of Zuckerberg's claims that Facebook users own their data, users - and non-users - have no way of determining the full trove of data that the company stores on an individual.