When watching the Developers video, don't look simply at the guy on stage, look at the audience. There is where the interesting stuff is going on. Thousands upon thousands, an entire concert hall filled with em. Keep in mind that these are just the developers who were at the company's 25th anniversary celebration, likely only employees. Microsoft enjoys a larger developer network than any company has ever seen.
So, when you see Ballmer screaming his chant to the assembled audience, consider this: open source has managed, with largely a self assembled collection of disparate developers, many only workng part time, to utterly defeat microsoft in the server room. How?
Developers. Developers. Developers.
Really damn good ones. I'd say that Ballmer has a good reason to sweat.