But the flip side is, as soon as they stop investing in expansion, the market will immediately start to wonder if their P/E is justified and might cause a decli

But the flip side is, as soon as they stop investing in expansion, the market will immediately start to wonder if their P/E is justified and might cause a decline in price. The signal from the market to Facebook now is that the shareholders want to invest in growth. And given FB's dominance, size, and talent, it's hard to argue otherwise. Facebook could still change a lot, and I think we're only seeing the beginning of social sharing/search/commerce/media into our lives.