Open Source software strikes at the heart of Microsoft, it offers for free the software that Microsoft sells and that is the basis for its enormous revenue stream.

This relationship is a Gambler's Ruin Competition, the rivalry between two parties, one with a large, well established position and the other with a small position but able to compete effectively on individual transactions. The classic example is a casino versus a professional gambler who has a system (a martingale) that enables them to win more than 50% of the time.

Microsoft might see a rapid reversal of fortune if a few strategic buyers go Linux. These would be big enough Open Source wins that they reverse the over-dominating share, the house advantage Microsoft holds in the market.