There is nothing like fully understanding the protections inherent within your vNetwork and the Roles and Permissions you can set within the virtualization management tool suites to ensure your vNetwork is secured, audited, and monitored for issues. Just like you do now within the pNetwork. Unlike the pNetwork, the vNetwork provides a certain amount of introspection and capability that is missing from a pNetwork, and this will also help with security.
In many cases when you start to discuss security of virtualization, you soon drop into a discussion of virtual networking, and management network security. In other words you are laying out the traditional security zones that exist within the networking world. Network security, virtual and physical, is extremely important however there is more to virtualization security than just your network. Here are some new ways to consider virtualization security.