Comprehensive write-up about the history and technology of virtualization...and, ultimately, I believe Intel's virtualization (VT) and LaGrande (LT) technology is the reason for Apple to switch to Intel processors....
And this snippet:
"...The newest Sun reincarnation of these concepts is (tentatively) called "Zones": a feature in the upcoming Solaris 10. According to Sun, the concept is derived from the BSD "jail" concept: a Zone (also known as a "trusted container") is an isolated and secure execution environment that appears as a "real machine" to applications. There is only one copy of the Solaris kernel..."