Thanks for a great write-up again Monique. I am hardly an expert in the subject but not surprised at the lack of agreement between various thought-leaders regarding "virtualization ". As you have correctly pointed out, it probably depends on the definition, flavor and vision of "virtualization". Loads of stuff out there that are still in developmental phase; for example the Turtle project (http://www.usenix.org/events/osdi10/tech/full_papers/Ben-Yehuda.pdf) addressing Nested Hypervisor model. In context of SDN the implications on performance, management (centralized or not)etc. are indeed up for discussion. Things such as CPU (e.g., instruction-set) virtualization, Memory (MMU) virtualization, I/O virtualization etc. perhaps bring into discussion usability of hardware and paravirtualization where applicability of API's may come into play....lots of open questions, discussions, philosophical and technical queries. Despite all that, SDN driven cloud is perhaps on its way to becoming the tech of 2014 (actually just heard JC say that somewhere...:-))...And when I read what I have written here, even I get a head-ache. So here's hoping you don't really read this :-)

With Respects, Always

santanu