I know little about FB's finances, but usually the way this works is that a young, successful company spends like crazy, sales go through the roof, and they keep spending - investing in the business - to try to vault to the next level.
Only when it becomes clear that the 40% sales growth will fall to single digits will the company start reigning in costs, and then earnings will go through the roof. So investors make models predicting when that turn will come.
It makes sense- why should a young company with the best product among its peers, growing at 40% per year slow down? Why shouldn't they take the opportunity/chance to build something completely collossal?
Your preference would be for them to say 'ok, we're good. We need to produce earnings, so we'll give up on all these promising projects."
Is tht really what you want them to do? so boring.
You're right that giving up on massive growth at this point (and reigning in the accompanying spending) would not be a good idea. But "boring" has nothing to do with it.