I worked in an R&D group at FSU back in 2003 making webmaps. When google maps came around, I spent a week deconstruction its inner workings. The tiling was such an obvious solution, but no one else was doing it yet.

Our next rev of the mapping software included tiling and progressive tile loading. We started with a commercial backend for creating the tiles (ESRI ArcIMS), and eventually switched to an open source solution (UWM's MapServer). Last I heard they had an entirely open source stack (MapServer, OpenLayers, gdal, etc).

Anyways, when I realized that Google had cached each and every one of these tiles - at every zoom level - I was simply confounded. It was the first time I actually contemplated the scale of a company like Google.