Ken Hess, wrote a piece that ridicules and derides anyone who doesn't virtualize literally all, as in every last one, of their servers. No, I'm not exaggerating. Here is a particularly striking part of this gem of technical writing. It's the summary for the entire article, no less: "You'll need to keep some physical systems around for those workloads that can't go virtual. And, be sure to keep a horse and buggy around when that whole automobile thing doesn't work out too."