I'm going to guess it's just a result of just using the best tools for the job. His developers know the MS stack, so it makes sense to build the application on

I'm going to guess it's just a result of just using the best tools for the job. His developers know the MS stack, so it makes sense to build the application on top of that. Things like Redis and HAProxy are traditionally better left to run on a *nix server. I use MongoDB on Server 2008 for testing and whatnot, but once that goes to production it's going into a Linux box. That the opposite isn't generally true (a mostly FOSS project using Microsoft bits) is a testament to what's available on the FOSS side, of course. Your use of the word "loyalist" implies some kind of blind joined-at-the-hip fanboysm is at play on Spolsky's brain. I think that's probably very far from the truth. Those of us who use and take advantage of Microsoft technologies are also quite capable of recognizing that some things are better done on other platforms. I.e., best tool for the job.