http://seer.entsupport.symantec.com/docs/340091.htm
In the doc above, "Basic Disk" DSUs are supported in a VM. But other more complicated disk stores, like Advanced Disk and Media Server Dedupe Pools (MSDP) are not yet officially supported in VMs for reasons that Christoph mentions above.
For comparison, there is a PureDisk Virtual Appliance available for VMware. They have set minimum and maximum requirements, like dedicated RAM & CPU, and maximum storage pool sizes. Such boundaries have not yet been identified for MSDP in VMs.
In other words, use at your own risk at this time.