All of our clients who have been using Microsoft SQL Server as a database have been converted to SQL Azure, Microsoft’s cloud database system.
Unlike SQL Server, Azure is not an application run on a single machine. There is no “server”, it is truly a set of servers that work in conjunction with eachother, but not in dependance of one another. This means that they can pull a machine out of the grid and pop a new one in with no down-time.
Moreover, it is not running on a Windows operating system, it is actually a system in itself, designed 100% to be a database cloud rather than just a virtual machine.
With SQL Azure, you lease database space rather than an individual machine. You don’t need any of the normal maintanence that a SQL Server machine needs. Microsoft manages the entire data cloud, and they do an excellent job.