Zuckerberg is also expected to be asked about Russia's use of US social media during the 2016 elections - a subject of several congressional investigations and special counsel Robert Mueller's probe into Russian interference.
Facebook, he said, do not generally ask people about their political orientation when they're joining the company."Mr. Zuckerberg, do you feel its your responsibility to assess users, whether they are good and positive connections or ones that those 15 to 20,000 people deem unacceptable or deplorable?"
"Zuckerberg is conciliatory in his presentation", said Mariann Montagne, portfolio manager at Gradient Investments in Arden Hills, Minnesota.
Publisher, platform, or a bit of both?
In a rare light-hearted exchange during his public grilling before USA senators Tuesday, the Facebook CEO told Sen. All Groups API will now on need approval from Facebook and an admin to ensure they benefit the group.
When Lee asked if the company was putting its "thumb on the scale" of communication categories outside the hate speech, terrorist organizing, nudity, threats of physical violence and bullying that Facebook regularly seeks out and removes from its site, Zuckeberg replied simply, "Senator, no". Ted Cruz (R-TX) over whether Facebook considers itself a "neutral public forum".
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 U.S. President Donald Trump's election campaign among its clients.
On Monday, Facebook began alerting people who had their data accessed two and half years after the incursion.
Facebook users more anxious about privacy
"Senator, no, I would probably not choose to do that publicly here", he said.
However, this data was collected for the purposes of helping U.S. campaigns, focused on USA users. The controversy has raised questions about whether the social media giant does enough to protect user information.
Under questioning by Senator Cory Gardner (R-Colorado), Zuckerberg admitted there was a hack of Facebook in 2013, when several employee computers were infected with malware.
So no - Facebook isn't listening to you through your phone to serve you ads.
NSA whistleblower Edward Snowden had something to add to that revelation.
He went on to elaborate that Facebook does have access to audio when people record videos on their devices for Facebook, but otherwise it doesn't access your microphone.
"My top priority has always been our social mission of connecting people, building community and bringing the world closer together", he said. "Here is what everybody has been trying to tell you today, I say this gently, your user agreement sucks".