If Open Source software is free, then why bother spending money on Microsoft Partner stuff? I already know what Microsoft's detractors will say: "There's no reason whatsoever. $40 billion per year is totally wasted."
This, however is not a very satisfying answer, simply because it doesn't quite ring true. Otherwise there'd be a lot more famous Open Source billionaires out there, being written up in Forbes Magazine or wherever. And Bill Gates would've been ousted years ago.