1) I think the word "loyalist" was poorly chosen on my part. I meant it only to describe how Fog Creek has traditionally been a fairly Microsoft oriented shop... even after (in my opinion) open source languages/platforms began to surpass MS in usability, documentation, and community support.
2) While it may be the case that it is not necessary to use MS technology to be featured in Bing searches, I think you (Joel) are among the more influential developers in the world and that your firm leverages Microsoft's latest technology was likely a factor in the decision to "feature" the results instead of simply displaying them first when they're relevant. Maybe I'm cynical but that seems like a smart marketing move on Microsoft's part.
3) My mention of license pricing was intended to include all licensing costs, including SQL server. I'd guess the cost of your setup as described would be about $150K in licenses... Perhaps rounding error but still a nice developer salary.
4) No disrespect or insult was meant by my comment. I started out using 100% Microsoft tools and technologies, and I've been intrigued to see open source projects start to offer compelling value and features. Mostly my comment was intended to express surprise that it's not simply a matter of "rounding error" costs to do a 100% Microsoft solution for a major site... and that things like Redis and Ubuntu are part of the reason that StackOverflow is as performant as it is.