That's the old argument: Rabbits are faster than foxes because rabbits are running for their lives, while foxes are only running for their dinner. For the sake of an interesting discussion, I would like to point out a flaw in applying this logic to FB vs. Google.
The dinner/life argument is true when we observe creatures that have co-evolved over a long period of time to reach an equilibrium of sorts in an ecological niche. Foxes catch some rabbits, but not enough to wipe them out, and not so few that foxes starve.
However, along the way there may have been other predators that starved to death because they couldn't catch any rabbits. And other prey animals that couldn't run fast enough and were wiped out. If we travel to a new ecological niche like a volcanic island that has risen from the sea, and there we observe one fox chasing a rabbit, it isn't a safe bet that the rabbit will escape the fox. We don't have evidence that foxes and rabbits are in equilibrium on that island, with both species able to eat enough and live long enough to reliably produce offspring.
Looking at Facebook and Google, we are not talking about the business equivalent of evolutionary time, and we are not talking about whole classes of businesses. Even though Facebook is running for its life, Google can easily wipe them out, just as on our volcanic island, one fox might easily eat one or for that matter all rabbits.
Footnote for the curious: https://secure.wikimedia.org/wikipedia/en/wiki/Ilha_da_Queim...