Virtualization is a great thing. It enables high availability, business continuity and server consolidation scenarios that we never thought possible in our hardware bound days. But one thing I find that doesn't get enough attention when people start moving to virtualized solutions is security.
This isn't a good thing, since the host operating system is a single point of failure for potentially dozens of virtualized instances on a single machine. Because of this, and more reasons, security is even more important in a virtualized environment as it is in a purely physical environment.
To get you up to speed on virtualization, here's a nice article on planning for Hyper-V security:
Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer