But if Microsoft were split into divisions (Windows/Mobile/Tablets, Enterprise/Office, Xbox/entertainment, Bing/Hotmail somewhere?) that could freely compete, it's actually pretty easy to imagine suitable CEO's for each one.
I'm truly hard-pressed to think of any value Microsoft as a conglomerate of these divisions, actually provides, strategy- or synergy-wise -- at least that's visible to those of us outside the company.
But is there any kind of precedent for this? It's common for companies to spin off a division, but I can't think of any company voluntarily truly breaking itself up like this. It's hard to imagine a board saying, "we admit we're not providing strategic value here, let's break ourselves up".