Well such a mistake would it hurt their ability to communicate with the analysts and the markets. They'd have less credibility and would have a harder time exp

Well such a mistake would it hurt their ability to communicate with the analysts and the markets. They'd have less credibility and would have a harder time explaining anything tricky. They may hear less about what investors do and don't think and what drives the stock's movements. Over time those communication gaps can lead to more volatility in the stock and perhaps lower levels. That may not matter to Facebook until it needs capital. But it will matter to early investors and employees holding stock they'd like to liquidate. Some of those players may have such returns they don't care, but not all of them are so fortunate and in general it's a missed maximization. How important all of that is depends on what FB wants to do and be. More broadly, public markets are an important constituency, if those investors don't trust you that's going to influence your reputation in the media and with the government.