I didn't mean to imply that you had to have the culture baked on day 1. But by the time you've moved beyond cofounders and are making hires, you better be well on your way to having it defined. Or you're doomed to wallow in misfits and repairing poor hires instead of moving rapidly.

And I totally agree that the founders drive and define the culture. It's their responsibility to establish it, manage it, and change it, if need be.