Facebook CEO Mark Zuckerberg testifies before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington. (Andrew Harnik/AP Photo)
Facebook CEO Mark Zuckerberg, left, testifies before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington, Tuesday. (Andrew Harnik/AP Photo)
Sen. John Thune, R-S.D., center, questions Facebook CEO Mark Zuckerberg as he testifies before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill. (Andrew Harnik/AP Photo)
Sen. Jerry Moran, R-Kan., left, accompanied by Sen. Ben Sasse, R-Neb., right, takes a photo as Facebook CEO Mark Zuckerberg testifies. (Andrew Harnik/AP Photo)
Sen. Bill Nelson, D-Fla., right, accompanied by Sen. John Thune, R-S.D., left, and Sen. Chuck Grassley, R-Iowa, second from left, speaks as Facebook CEO Mark Zuckerberg testifies. (Andrew Harnik/AP Photo)
An audience member wearing a blue and green pointy wig, aiming to look like a Russian troll as Facebook CEO Mark Zuckerberg testifies. (Andrew Harnik/AP Photo)
Members of the audience hold up signs and wear sunglasses that read "Stop Spying" before CEO Mark Zuckerberg arrives to testify. (Andrew Harnik/AP Photo)
Facebook CEO Mark Zuckerberg arrives to testify before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington. (Pablo Martinez Monsivais/AP Photo)
Facebook CEO Mark Zuckerberg arrives to testify before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington. (Andrew Harnik/AP Photo)
Facebook CEO Mark Zuckerberg testifies before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington. (Alex Brandon/AP Photo)
Facebook CEO Mark Zuckerberg arrives to testify before a joint hearing of the Commerce and Judiciary Committees on Capitol Hill in Washington. (Pablo Martinez Monsivais/AP Photo)
Advocacy group Avaaz placed 100 cardboard cutouts of Mark Zuckerberg outside the U.S. Capitol in Washington on the day of his testimony to Congress. (Kevin Wolf/AP images for AVAAZ)
Advocacy group Avaaz placed 100 cardboard cutouts of Mark Zuckerberg outside the U.S. Capitol in Washington on the day of his testimony to Congress. (Kevin Wolf/AP images for AVAAZ)
Facebook CEO Mark Zuckerberg testified before congress after a privacy leak that affected millions of users.