You said "The early days of virtualization (when servers were virtualized) provide a cautionary tale. Server virtualization lowered CapEx but led to skyrocketing operational costs because much more complex processes - hence highly-skilled staff - were required."

Apparently, the other reason why server optimization via virtualization can experience diminishing returns over time is due to the fact that some of the significant initial savings (from eliminating excess hardware, etc) can't be sustained via the ongoing use of the software. Plus, rising software license renewal fees for traditional virtualization further reduce the potential for incremental savings -- unless you switch to a open source hypervisor with a subscription model.

Therefore, I'm wondering, are the savings from network virtualization likely to be subject to the same sort of diminishing returns over time?