Since this post was written , Vmware have included USB passthrough in its most recent version 4.1
The VMware Virtulised Operating systems ESXi and ESX do not support USB passthrough. VMware has stopped USB passthrough, as ESX was designed for VMotion. You can migrate Virtual Machines between physical servers and no one will notice. USB will prevent this, since VM is locked to physical USB port.
This brings a problem for Small Business’ when it comes down to their backup solutions. Large Enterprises will use SCSI or SAN which are compatible with VMotion. Luckily this problem has been resolved using a device from Belkin.
The Belkin Network 5-Port USB2.0 Hub maps up to 5 USB devices over a normal TCP/IP network for you. Installation is simple and once installed on a machine will immediately detect the plug and play devices connected to the HUB
This device will also solve issues with servers needing to access USB Dongles with hardware keys on them for anti piracy reasons as seen here
The cheapest I could find was one on Amazon for £52 including free postage