Many smart "kids" (gee, thanks dad, glad you know what's best for me!) want to solve interesting problems, not muck around with all that other stuff you have to deal with as an entrepreneur.
As for Google - it's what you make of it. I know some people who've gotten stuck in a narrow corner of the company, but I've personally been exposed to a pretty deep cross-section of the search stack, and worked on some fairly exciting projects. Working for a big company doesn't excuse you from actively managing your career - if something exciting is coming up, volunteer for it! And nobody can stop you from working on other stuff - if there's something interesting, just go hack it up and ask for forgiveness later.
This is probably the best advice given on hacker news today.