Over in the real world, working for an employer like Google is a risk hedge. If your idea for a project this quarter turns out to not be useful, you don't run out of money and end up living in a cardboard box. You learn from your experience, try again, and your family gets food on the table. You can say it's childish to hedge risk, but you can also say it's very adult to hedge risk. Maybe you are a super genius that can code up a solution to a really hard problem all by yourself. But what if the market doesn't like it? Too bad, you're in the same place as the guy who sits at home all day, smokes pot, and watches daytime TV. The market decided: you suck.
I agree with Aaron that we could always use more computers. Sometimes during peak hours, the batch scheduler will only give me a few hundred machines to run my MapReduce on. What am I, a farmer?
Ultimately, I like working at Google and I like having toys in the office. I have Nerf guns. I use Hakase from Nichijou as my profile picture. At the same time, I feel like I'm doing impactful work, with some very smart people. And I feel that I'm evaluated (and compensated) fairly. Does that make me infantile? Maybe so. But I like it.
My real fear of leaving Google is the time I'll have to spend writing all the infrastructure from scratch. And finding someone else that can afford my hourly rate.