Mark Zuckerberg finished his second day of voluntary testimony in front of Congress today. Earlier this week, I was interviewed by the Associated Press about what he should do to prepare, and it appears he was given similar counsel and followed it. A few things about the hearing that stood out:

1. Zuckerberg was mature, polite, and contrite, and he patiently explained (over and over) the complexity of Facebook’s business.

2. Zuckerberg was relaxed, well-prepared, and comfortable; if not particularly commanding, which given his age as compared to the members of Congress was an appropriate tone.

In the end, Zuckerberg did what he needed to do…

3. Zuckerberg acknowledged Facebook’s mistakes and appeared earnest in his promise to repair past ones and prevent new ones.

4. Obviously, additional regulation is coming, and Zuckerberg was clear that he wants Facebook to influence it. Interestingly, he also warned Congress to be careful about unintended consequences of regulation precluding competition (“Facebook can afford to comply with regulations but tech start-ups and less rich companies will have a more difficult time…”).

So, other than a few brief moments of significant contention between Zuckerberg and members of Congress (like these noted below), Zuckerberg’s performance gets an A.

Representative Kathy Castor (D-FL) grills Zuckerberg earlier today. Zuckerberg responds politely — but sternly — and successfully neutralizes her venom.

Senator Dick Durban (D-IL) crosses the ‘T’ yesterday on the privacy issue by posing some mild personal questions to Zuckerberg.

Senator Ted Cruz (R-TX) questions Zuckerberg on the company’s position as a neutral provider of information or a corporate entity with its own constitutionally-protected right to freedom of speech and a political point of view. As this goes to the heart of Facebook’s business model and the regulatory scheme that might influence it in the future, it was a moment (similar to Durbin’s) that made Zuckerberg squirm.

In the end, Zuckerberg did what he needed to do, which was: a) leave the hearing without creating more damage to the Facebook brand or his own future credibility in leading the company; and b) position himself and Facebook as influencers on any future regulations or legislation — a function of how the company operates now in the immediate wake of the hearings.

As a final testament to Zuckerberg’s success, Facebook stock increased in value yesterday; Zuckerman ultimately made $2.8 billion just sitting there.