Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
As a technology writer, I use virtualization all the time, primarily to review new Linux distributions without taking up an entire machine's worth of data and resources. For everyday users, virtualization seems to be an unneeded luxury than anything else. Why would you need to run two operating systems at the same time?
I can think of three good reasons why virtualization on the desktop is a good idea.
Security. One of my favorite recommendations for all users is to install Linux as their primary desktop machine, saving their personal data on an external drive before they do. If they have Windows applications that they simply cannot part with, then they can use a virtual machine application to install Windows, and re-install just the needed apps. Then they're off, moving their saved data back onto either the native Linux system or the virtual Windows machine, as needed. This gets them the flexibility of the apps they need, while letting them connect to the Internet on a much more secure and stable platform.