The real concern (which Google can't fully solve) is housing. If you add 10k or 20k more employees in these beautiful new offices, where do they all live? I guess Google could build apartments too but that's not ideal, I don't want to live at work.
I currently commute to MTV from SF. I have a shitty apartment, i pay 2x as much as it's worth in any other city, and I commute 1.5hrs each way on a clogged highway. I hope it's doesn't get much worse.