I can't think of any topic in the field of privacy that has been more polemicized and politicized and distorted than discussions about the Patriot Act. Most discussions about it are simply factually and legally wrong. I respect Microsoft for blogging and explaining this. It takes courage to talk about this issue, since so many people around the world have passionate reasons to want to resist or restrict the power of (some, all, or just the US) governments to use valid legal process to access data.
Over and over again, I read about people and politicians around the world saying that they want their data to be stored in the cloud (i.e., in a data center) in their country/Continent, so that it's protected from American law enforcement under the Patriot Act. This is a common refrain, for example, in Europe and Canada. Indeed, it has given rise to an entire industry purporting to offer "euro-clouds".
Therefore, it's perhaps surprising for some people to learn that the location of storage of the data has no impact on this issue, with regards to US-headquartered companies. It has limited impact on this issue, with regards to non-US headquartered companies. I won't repeat the legal analysis, since Microsoft's blog did a good job in explaining it.
It's well-known that global cloud-service providers maintain data centers around the world, mostly to ensure that their services operate with efficiency, speed and reliability. But they don't, and can't, operate as tools to evade or circumvent valid US government access to information, whether under the Patriot Act or any of its related/predecessor laws, since the location of data within the cloud is simply not a relevant legal factor. I know that's controversial, but it's also a legal fact, so kudos to Microsoft for saying it publicly.