>>14 Google isn't just a search engine. It has investments in and has made advancements to most of the major fields (health, space, computer tech, internet (/social media now, thanks to G+), automotive, etc.). I believe it's having ties to 7 (?) major industries and a net profit each year of at least 11 (?) billion that officially recognizes a company as an industrial superpower. They're literally everywhere.
Facebook has been trying to join them in the rankings by spreading their interests and power out over different industries and following varied goals. In the end, I think it's just a matter of competition between employees. Google has already contracted a lot of the really great people in the tech industry, which is leaving Facebook with a lot of the 'newer recruits', if you will. I personally think that's the only thing keeping them from joining Google as a superpower within the next decade, but if they're still around in a couple decades, they may join or even surpass Google (if Zuckerberg chooses to go that far).