If you're suffering from virtual server sprawl, it may be difficult to keep track of all your VMs, and it may thus be difficult to ensure that all of them are properly patched. Also, hypervisors do not perform encryption, leaving open the possibility of man-in-the-middle attacks such as Xensploit, which intercepts unencrypted data when VMs are migrated between physical servers.That doesn't mean you should avoid virtualization altogether, but it's often best to start with minor systems and work your way up to mission-critical applications.

5. Desktop virtualization will save me money right away

Virtualization should make it easier to deploy new desktops to users, apply patches and perform other management tasks. Desktop virtualization can also save money in the long run. A Denver transportation agency is expecting a over eight years by purchasing thin clients that will last longer than traditional PCs.

But IT shops have to remember desktop virtualization requires significant upfront costs, from purchasing user devices such as thin clients to back-end infrastructure such as servers, PC blades and networked storage to support VMs.

Anecdotally, Forrester Research analysts have found that enterprises spend about $860 per user, plus network upgrades, to get a desktop virtualization project up and running in the first year. A well-done desktop virtualization can certainly cut long-term costs. It just might take a few years to achieve ROI.