The Danger of Overusing Virtual Machine Replicas
One of the most heralded features in Windows Server 2012 (previously known as Windows Server 8) is support in Hyper-V for virtual machine replicas. If you're familiar with VMWare it's similar to Site Recovery Manager, for Xen you're probably looking at Remus, and Kemari for KVM (bear in mind that none of these products are necessarily exactly the same, but close enough).
Virtual Machine replication across sites is very attractive. You get a lot of flexibility with minimal effort.