I see.
I would think this would be relevant for proxies/fileservers etc if you want to use dedicated network-cards, diskcontrollers, tapestreamers etc for servers.
I'v done this before in xen (allocated raid-controller and network-card to a fileserver-vm) for maximum performance and isolation.
What I'm looking for is the ability to build a media-server with dedicated hardware for multi-client streaming, based on virtualization.