Zuckerberg faced tougher questions from House lawmakers over Facebook's stance than during Tuesday's five-hour session in the Senate, where his defense of data sharing was weakly challenged. And in the past, Facebook has described various forms of data collection that don't involve users directly giving it to the social network.
The shares fell steeply last month after it came to light that millions of users' personal information was harvested from Facebook by Cambridge Analytica, a political consultancy that has counted US President Donald Trump's election campaign among its clients.
Speaking in the wake of a scandal over the massive leak of data to a British political consultant, Zuckerberg reiterated that the company had shut down the pipeline that allowed such data, including his own, to slip into the hands of third parties.
"While Facebook has certainly grown, I worry it has not matured", Walden, R-Ore., told Zuckerberg.
"He said he's in favour of some kind of regulation, but he's not behind some kind of sweeping regulation of Facebook that some critics of the company would like to see", McCabe said.
■ Remember when you had to be a college student to use Facebook? The reason why Senators were so focused on this is because an ad-free version would ultimately involve less of users' data being taken. Republicans pressed him on whether Facebook suppresses conservative views. Facebook encourages campaigns to do this.
At $5.12, Facebook's current CPM is not the most expensive among the major social networks - LinkedIn's $16.99 is - but that likely reflects the employment and recruitment advertising market norms, versus conventional consumer marketing.
"Diamond and Silk was deemed "unsafe".
In both hearings, legislators pushed Zuckerberg on its potential monopoly power. "So my position is not that there should be no regulation but I also think that you have to be careful about regulation you put in place".
"I am optimistic that, over a 5-10 year period, we will have AI (Artificial Intelligence) tools that can get to some of the nuances - the linguistic nuances of different types of content..."More news: Arsenal were on the ropes against CSKA, admits Wenger
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According to Zuckerberg, the company has 200 people working on efforts to combat the promotion of "extremist" content.
Zuckerberg did not provide the names of who else may have bought Kogan's data, which came from a personality quiz app Kogan developed for Facebook, and told lawmakers he would follow up with them about that.
"It's pretty obvious to me that someone is listening to the audio on our phones", Buschon said.
MARK ZUCKERBERG: Congressman, in general, we collect data from people who have not signed up for Facebook for security purposes.
Yet before 2014, Facebook didn't offer some of the estimated 87 million victims, whose shared data could have include private messages, the courtesy of refusal.
The company has always denied these allegations.
Facebook tracks "certain information for ads and security". He assured senators the company would handle the situation differently today.
Lujan rightly went on to point out that, "You've said everyone controls their data, but you're collecting data on people that are not even Facebook users who have never signed a consent, a privacy agreement".
Near the end of the session, Debbie Dingell, a Democrat from MI criticised Zuckerberg's lack of knowledge of his own company. The CEO replied that he doesn't know.