Xen provides the capability to run multiple OS's on a system.
But what about running the same OS on different hardware platforms? Can't the virtualization work both ways?
Not being tied to a particular system could be advantageous, especially if you wanted to migrate from x86 to a Cell-based system, for example. You wouldn't have to change your OS and all of your apps, just change the microcode (an old IBM term)
That could negate the need for the prereqs of an application specifying hardware.
Just specify XEN.