Many Microsoft servers are powered by Linux

AFAIK, the servers itself are all-microsoft, most brobably netcraft.com is confused by load-balancers (akamai or something similar)

The "Linux" servers are Akamai's.

This has been going on since windows NT launched (as in, that's when people first found out). They just outsource a lot of their website load to external hosts who run Linux.

Akamai isn't Msft they just have subdomains pointed to it

Talking about "dogfooding" <a href="http://en.wikipedia.org/wiki/Eating_your_own_dog_food" rel="nofollow">http://en.wikipedia.org/wiki/Eating_your_own_dog_food</a>