Truth be told, no one really cared about the desktop before we started talking desktop virtualization.  If a desktop failed, it really only impacted a single user, not a big deal unless the user is the CEO or Payroll. Unfortunately for that user, they could be out of commission for days/weeks.  But in a desktop virtualization world, that user can automatically reconnect and get their desktop back, albeit it is technically a different entity as it is now running on another hypervisor with a fresh OS install and Apps, but it looks and acts the same.

What happens if there is a major glitch, issue, failure, etc with the environment?  Even if your environment is rock solid, someone is going to do something that will bring down a very critical component. You might lose one user, but chances are you will lose hundreds or thousands.  If the failed component is critical, those users might not be able to reconnect.  Now you are in a world of pain.  If you are in IT and in charge of the desktop virtualization solution, it might be time to either
1.    Change your name
2.    Update your Resume
3.    Convince everyone that you are trying to save energy costs and shut down the entire system (not likely to work)

How do you avoid the name change or career change?  By doing your job correctly and designing a desktop virtualization solution that can withstand the failure of components without denying user access.  A High-Availability Reference Architecture and Implementation Guide for XenDesktop have been released to the Ask the Architect site.  

The choice is yours, design an environment that has high-availability or design your own rapid exit plan.  
Daniel – Lead Architect – Worldwide Consulting Solutions