Ever since Hyper-V débuted, and Virtual Machine has been supporting x64 architecture, people have been thinking about running SBS 2008 in a Virtual machine. In fact, many of our beta testers have been running Virtual copies of SBS 2008 for some time now. The question always was "is it supported". While official support is still pending based on any copies of SQL included in the machine, a tentative plan has been posted over at the SBS Official Blog.
Looks like there will be three scenarios:
1) Virtualizing the SBS Standard Server
2) Virtualizing both the Standard and Premium SBS servers
3) Keeping SBS Standard Physical and using Premium as a Virtualization Parent
Let me know which one you're most excited about! To learn more, read the Official SBS Blog post on Virtualization.