Last night's session also revealed that Zuckerberg himself doesn't know how long it takes Facebook to remove all of your data once you choose to leave the platform and admitted that the company keeps a backup of data for an unspecified short period of time.
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.
"How can consumers have control over their data when Facebook does not have control over the data?" asked Rep.
"In general we collect data on people who are not signed up for Facebook for security purposes", Zuckerberg said Wednesday in a hearing about the social network's privacy practices in Washington before the House Energy and Commerce Committee.
The 87 million Facebook users had their data harvested by a third-party app posing as a personality quiz.
Seven Iranians were killed in strike on Syrian air base - Tasnim
A US Navy guided-missile destroyer, the USS Donald Cook, is in the Mediterranean. It has since spiralled into a complex war involving world powers.
Zuckerberg, wearing a dark suit instead of his usual gray T-shirt, navigated through the first hearing on Tuesday without making any further promises to support new legislation or change how the social network does business, foiling attempts by senators to pin him down.
Facebook began informing users this week as to whether their private data may have been wrongly shared with Cambridge Analytica. I don't know what information was leaked out and what it means to my Facebook.
"Every piece of content that you share on Facebook, you own, and you have complete control over who sees it and - and how you share it, and you can remove it at any time", Zuckerberg told Hatch. For the past 14 years Facebook has been much more interested in exploiting the personal data rather than protecting personal data. "In retrospect it was clearly a mistake to believe them", he said.
Rep. Marsha Blackburn (R-TN) had the chance to ask the Facebook CEO himself, Mark Zuckerberg, why the company targets certain content.
Democrat Bobby Rush was in the process of asking Mr Zuckerberg when he learned that Facebook allowed advertisers prevent ads from being shown to certain minority groups, a possible violation of civil rights laws. She said "Facebook was surprised we were able to suck out the whole social graph, but they didn't stop us once they realized that was what we were doing". Facebook generatesabout $9 a month per user in the U.S.by targeting you with ads. "There were a number of other researchers who were building similar apps", Zuckerberg replied.