One year ago virtualization.info published a report called Virtualization Industry Challenges, which describes the major issues that a customer has to address when embracing virtualization.
The very first one was (and still is) the lack of support.
Andrew Dugdell points at a critical VMware document which summarizes how customers can receive support for Microsoft software installed inside virtual machines.
Reading it gives the impression that there are an endless number of restrictions but Microsoft actually is one of the best at supporting the virtual environments.
Obviously this is just the tip of an iceberg.
Some major vendors are so hostile to virtualization that have to invent their own hypervisor to allow their products inside VMs.
Others simply prefer to ignore virtualization completely.
It seems impossible that DMTF is working on interoperability standards to manage virtual machines when the market cannot even agree on a way to provide interoperable support for them.