For those who didn't read up on it yet, Microsoft is embracing open source for Windows Vista, Windows Server 2008, SQL Server 2008, Office 2007, Exchange Server 2007 and Office SharePoint Server 2007.

Well, not exactly, anyway. They are just releasing API documentations, most of them already available elsewhere. Though people are not wrong in that Microsoft is not leaving out the OS path completely out of the question. And this is within reason.
In the "greater ends", and as Internet gets even more popular and diversified even to John Neverusedacomputer, Open Source is and will be more popular. It's the matter of Free To Use vs Pay For It. In most case, this big difference gives a better opinion of it.
Microsoft is afraid of Open Source, this is no secret. It has the power to bring down any paying version of what is made, with a right tactic. Hell, in the next years, Linux will be more and more adopted as companies understand Ubuntu is far beyond the point of "desktop-ready" and vista is just not "notebook-ready".
Microsoft wants popularity. They want their part of the FOSS cake. Their move just proves they are scared, just like the Yahoo! bid did a few weeks ago. I'm not blaming them for doing it, just taking it with a grain of salt to demonstrate the obvious.