Why There Will Never Be Another Red Hat: The Economics of Open Source – Andreessen Horowitz is a perfectly-sound article from a pure “profit-only” point of view.
What the author misses is that Amazon infrastructure is overwhelmingly built on Free Software, that even companies like Microsoft and Oracle put lots of development efforts into Free Software projects such as .Net – yes, it as been released under a non-persistent BSD-like license, AFAICS – or MySQL or Java.