There is no requirement to maximize short-term stock prices, though. He may genuinely believe that his strategy is long-term the correct one, in which case he'd be correct to pursue it. After all, the stock price has widely swung in its evaluation of Facebook's value in a space of mere months, first pricing FB very high and then pricing it much lower, with little intervening change of fundamentals, so its credibility as an indicator of company performance is not strong.

Indeed. Bezos is famous for destroying short term profits because he likes to reinvest in Amazon (growing logistics, distribution, etc) which has so far profited investors handsomely in the long term.

But the major difference between Bezos' strategy with Amazon and Zuckerberg's apparent strategy with Facebook is that Amazon was absolutely up front that they're willing to sacrifice short term profits for long term stability.

Amazon's initial shareholder letters were basically "Yes, we know we're not turning a profit right now, but that's because we believe in our long term plan". They also detailed what they were doing to make sure that their short-term spending was going to result in long-term returns. Amazon's letters and SEC filings were focused almost completely on this message: That we're spending money now to make a LOT more money in the future.

Facebook, perhaps due to the competitive space that they're in, really haven't done anything like that. Their filings have more of a "Deer in the Headlights" feeling than anything else, with mobile revenue being basically 0, and not adequately explaining the massive expense increases for Q2 2012. Those are red flags for investors. It's a completely different message from Amazon's.

Is this true for an IPO as well? How can the CEO work for the shareholders before they buy the shares? Isn't the point of IPOs to get the most money for the company?

No. It was quite clear in the IPO that Zack is in control and can do what he likes. Dual share classes and full control. He has no obligation to do what is in the interest of other shareholders.