At a size of Google, the company has to be mostly constructed out of "cogs", to be resilient. If Google couldn't handle losing ~40 (as of right now) employees, that would be something seriously strange for one of the most valuable companies on the planet.
I'm sure there are sets of 40 employees that would cripple Google, at least be extremely unfortunate if they left together. There are certainly important components with a bus factor of less than that.
