Too big + too many smart and creative people = impossible to manage without being a complete dictator
Google is running into this. Their track record of late is spotty at best, and it's because their culture is too wild-west and "throw on wall, see if stick" style.
As much as geniuses are really good at solving problems plaguing modern society, they are really bad at focussing. They need leaders that understand them, like John Lasseter at Pixar. Alternatively, they need equally-genius benevolent dictators like Linus Torvalds (Linux, Git) to keep them in check. Failing that, they need supremely smart, pile-driving, and obliquely techie-cum-marketing obsessed leaders like Jobs at Apple.
Gates + Ballmer = those things above, but you really need one voice, not two. I think Google is having the same trouble having Sergey and Larry's style squaring almost diametrically against Eric Schmidt's.