Ben Thompson in this week’s excellent Stratechery article:

[…] culture is not something that begets success, rather, it is a product of it. All companies start with the espoused beliefs and values of their founder(s), but until those beliefs and values are proven correct and successful they are open to debate and change. If, though, they lead to real sustained success, then those values and beliefs slip from the conscious to the unconscious, and it is this transformation that allows companies to maintain the “secret sauce” that drove their initial success even as they scale. The founder no longer needs to espouse his or her beliefs and values to the 10,000th employee; every single person already in the company will do just that, in every decision they make, big or small.

As with most such things, culture is one of a company’s most powerful assets right until it isn’t: the same underlying assumptions that permit an organization to scale massively constrain the ability of that same organization to change direction. More distressingly, culture prevents organizations from even knowing they need to do so.