While I do believe that Linux stability as well as MS instability is generally exagerated, and I have run across hundreds of sites that are run from windows boxes, here is how I interprete the statistics presented...
The vast majority of small web sites don't care what platform they are running on as they are just putting up a few static html pages. The 8k sites that "migrated" from Linux to Windows are primarily of that nature. Sites where the creators neither know or care their platform, and just want an http server for their static html files.
