We've been using Microsoft Azure virtual machines for development for a while. This means we run our Visual Studio instances in the cloud up on special virtual machines that have nothing on them except the bare minimum required for writing software. This keeps different projects separate from each other, and also speeds up network access, which is useful for network-intensive applications.
We started noticing, however, that going to MSDN or Google or other big sites became...challenging. All of these sites started acting as if our VMs were located in Brazil, when we knew perfectly well that they were in Virginia. Microsoft has finally explained the problem:
IPv4 address space has been fully assigned in the United States, meaning there is no additional IPv4 address space available. This requires Microsoft to use the IPv4 address space available to us globally for the addressing of new services. The result is that we will have to use IPv4 address space assigned to a non-US region to address services which may be in a US region. It is not possible to transfer registration because the IP space is allocated to the registration authorities by Internet Assigned Numbers Authority.
At times your service may appear to be hosted in a non-US location.
It is important to note that the IP address registration authority does not equate to IP address physical location (i.e., you can have an IP address registered in Brazil but allocated to a device or service physically located in Virginia). Thus when you deploy to a U.S. region, your service is still hosted in U.S. and your customer data will remain in the U.S.
In other words, Microsoft's cloud service is so popular that they have run out of addresses to assign to it. Microsoft, it should be noted, has tens of millions of IPv4 addresses available. (Of course, IPv4 has only 4.2 trillion possible addresses, though fully 43 billion are in private IP ranges.)