This might be of use to somebody out there -- consider it an FYI...

Virtualizing Mac OS X Client with Oracle(!) [sic] Virtual Box http://reviews.cnet.com/8301-13727_7-20005524-263.html

Mac OS X Server has been a candidate for virtualization for a while, but as far as I know, this is the first for Client.

Disclaimer: I haven't tried this yet myself.