Personally I think the next wave of infrastructure efficiency will be driven by Linux container technology (LinuX Containers = LXC). The LXC container approach does not require a hypervisor - instead you run isolated "containers" on a Linux host. LXC provides operating system-level virtualization leveraging cgroups (control groups) to completely isolate the operating environment, including process trees, network, user ids and mounted file systems. This work was started by engineers at Google ...
