I think its better to use an embedded-virtualization software like
http://www.ok-labs.com/ or
http://wiki.openvz.org/Main_Page. Unless you have some other reason for doing so of course.
Would also be interesting to see if you can emulate the Plug's linux distro using the VirtualBox. This way it will be easy to test a lot of the functionality on the virtual box. I'm still waiting for the plug. Would like to play with the distro, etc.
Thanks,
PC.