Zuckerberg was on Capitol Hill for the second consecutive day to answer questions from Congress, visiting the House of Representatives after sitting with almost half the Senate on Tuesday.
Facebook has been consumed by turmoil for almost a month, since it came to light that millions of users' personal information was wrongly harvested from the website by Cambridge Analytica, a firm that has counted US President Donald Trump's election campaign among its clients.
Zuckerberg said regulation of social media companies is inevitable, but warned that rules could also hamper the industry's growth.
But Mr Zuckerberg pushed back on congress members' suggestions that users do not have enough control of their data on Facebook in the wake of the privacy scandal.
"When we learned in 2015 that Cambridge Analytica had bought data from an app developer on Facebook that people had shared it with, we did take action", said Zuckerberg.
The admission underscores the problem Facebook has in persuading lawmakers that users can safeguard their own information if they carefully manage their personal settings and that further legislation governing Facebook's use of data is unnecessary. 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. Lindsey Graham about whether Facebook is a monopoly, and today has also (so far) produced one good round of questions. "If so, how many times has that happened, and was Facebook only made aware of that transfer by some third party?"
Mr. Zuckerberg did not admit that the company explicitly chose to withhold that information from consumers, but he said the company made a mistake in not telling users. "First, I understand where that concern is coming from because Facebook and the tech industry are located in Silicon Valley, which is an extremely Left leaning place", said Zuckerberg.
Outside the Capitol Building on Tuesday sat dozens of cardboard cutouts depicting Mark Zuckerberg, the chief executive of Facebook, wearing a characteristic T-shirt emblazoned with the message "Fix Fakebook".
Zuckerberg didn't elaborate more than that during the exchange with Eshoo, including how much of his personal data CA obtained. "It was my mistake and I'm sorry", Zuckerberg said on Tuesday.
Tom Galvin's company Digital Citizens Alliance conducted a report that finds 71 percent of respondents lost trust in Facebook.
"Senator, I want to make sure I get this accurate, so it would probably be better to have my team followup afterward", Zuckerberg responded. Richard Blumenthal said he was "unsatisfied" with the hearing because it was "more of the apology tour, which we have heard before".
Graham demanded to know why Congress should let Facebook self-regulate.
Marcus Adeniyi is a freshman at East Stroudsburg University. he says he stays off most social media websites because it's too easy to get hacked.