Fuck Yeah Side Talking!
Just make sure they happen at night.
All your face are belong to us!
Why you would run Windows on top of Linux, given...there are now FOSS alternatives for almost anything Windows can provide
Even if that were true, in practice companies don't just swap out production environments because alternatives potentially exist. What works well for you may be problematic in even a slightly different environment. Others have mentioned apps for which OSS interoperability isn't there yet, and I'd add Group Policies and other AD centric tech to the list (although I admittedly haven't checked out recent versions of Samba lately, so maybe I'm wrong on that). I'm as big of an OSS advocate as there is, but part of advocating effectively is knowing where limitations exist and dealing with them rationally rather than sugar-coating them. I agree with the gist of what you're saying though, and there are a lot of shops that could lower TCO by exploring the alternatives.