The problem is, virtual machines are designed to be hardware independent - tying a VM to a machine specific USB device defeats that purpose and reduces transferability of the VM should it need moving.
Having an external USB host would be a better bet, as it doesn't matter which VM hosting box the guest VM is on then - the USB host still stays on its own IP.
As mentioned above, USB over network software would seem the best solution.
This video shows one in action on Hyper-V. http://virtualboytv.com/r2hyperv7.aspx
Citrix released Xen 4.0 last week, so it does now (along with VGA pass-through to HVM guests). :)
Originally Posted by RabbieBurns