Under the microscope, Zuck faces possible regulation, promises changes.
"Would you be comfortable sharing with us the name of the hotel you stayed in last night?"
"Um." Mark Zuckerberg paused while he considered the question by Sen. Dick Durbin. "No."
"If you messaged anybody this week, would you share with us the names of the people you've messaged?" the Illinois Democrat asked him.
"Senator, no, I would probably not choose to do that publicly here," Zuckerberg responded.