Microsoft has released Windows Server 2008 Foundation (a low-cost variant of the Windows Server 2008 core). Paul Thurrott covers some valid reasons for Microsoft releasing a product that is squarely aimed at tiny businesses (15 people or less) and in doing so they are also taking a broad swipe at the hardcore enthusiast market. Notably these are the two market segments that have a predilection towards the use of pirated Windows OS products (be it client or server) and with this release, Microsoft is making it even easier to go 'legit'. There are a couple of more reasons which I believe led to the release of this SKU.
1) The Worldwide Recession - Lets face it, the global downturn is not going to be kind to sales figures and Microsoft needed to pull something off that would keep those cash registers ringing (and in doing so keep shareholder value intact) well through this time of economic prudence.
2) Linux - This is actually related to my first point above. Companies not spending more often than not translates into companies looking to free software. Ubuntu has free fully supported enterprise server and desktop versions out every 6-months and they've got zero shareholders to worry about. That's the deep-seated Redmondian fear. I'm not even going to prod the 'TCO monster' with a 10-foot pole, but depending on how you look at it, the release of Server Foundation will likely act as a gravity well and pull those sitting on the fence back into the Microsoft product fold.
It will be interesting to see the final feature set of Windows Server 2008 Foundation. With no support for virtualization (as per the EULA I suppose) and single-processor-socket only support, I wouldn't look to it to run my "weather simulation" server, but as a low-end file/database server it seems like Microsoft may just have hit the sweet spot.