Google’s Chris di Bona on why they use open source throughout the company, and not just in their development stack:

It’s all about flexibility for us. The terrific thing about open-source software is that we don’t have to ask anyone’s permission before we make changes to our operating systems. We don’t have to ask anyone’s permission before we make changes to our databases. We don’t have to pay any per-client licence fees for these things. This is really important, not just from a cost savings point of view, but from a flexibility and speed point of view.

So the lesson? Open Source may be cheaper than proprietary alternatives, but having the freedom to do what you want when you want with your software is more important than saving a few bucks.