To cut it short - every system administrator needs it. Some examples of practical applications:
- Hosting - all ranges on the same platform, from low-level shared and medium-power virtual server to powerful dedicated servers - seamless scaling up in the same safe virtual private server.
- Server consolidation - put together your existing servers and use more powerful and reliable hardware.
- Increase availability - keep an up-to-date copy of your virtual private server on another server and start it in seconds in case of failure.
- Education - each student gets its own virtual server with root access.
- Testing - safe experimentation on the machine that runs other services.
- Clean sandbox - install each service in its own freshly created Virtual Private Server and you will never have to resolve dependency problems.
- Multiversioning - keep "snapshots" of the project you are working on and be able to switch back and forth in seconds.
- Improve network services security - run each server in its own Virtual Private Server. If an application has a security hole only this particular virtual private server will be compromised, never - the whole system.