Magnolia ain't exactly indexing every page on the internet though, ya know?
I agree with you that that is one of Google's key strengths, though. PageRank is neat, but the real edge is that the site is fast and the infrastructure is based on commodity hardware, so it's cheap.
The real edge is not that it's based on commodity hardware, but that it's based on scalable low-management software (I imagine all this, and skimmed their Google File System paper once. I don't work for Google).
It wouldn't matter if they were blades or Sun UltraWhatevers, the real benefit is that if one dies, nobody need panic - plug another in and "the system" will rebuild it. If a rack dies, plug another in and the system will rebuild it. If a datacenter dies, the others will cover for it.
No backup tapes, no manual tweaking each new build.
As its been said a million times before, hardware is cheap. Creating a system that can utilize the cheapest Celeron servers you have with the flick of a switch is what you really need to create.
Adding a few more servers is much cheaper than downtime.
I suspect their file storage system is simply good enough to replicate data intelligently across many machines/sites like a giant RAID array.
I also think that it's a truly massive benefit they have over other companies, particularly small companies, and that it's rarely discussed as such.