While it's true that in the case of hypervisors like ESX or Hyper-V the guest OS's are at the mercy of the hypervisor, it's still a better solution.
OS partitioning/virtualization techniques like Solaris Containers will never be popular (IMHO) because the
management is too difficult. Sharing the OS and it's files means that every container must be taken down and patched - at the same time! This is practically an impossibility unless all your containers have the same management cross-section. This may be the case for some specific applications (VDI perhaps?), but makes creating a general purpose virtualization platform difficult!
I realize some containers have tools to assist with migrating the containers - sometimes live, but mostly off - to another physical machine/OS instance. Analogous to VMware's "maintenance mode", but probably a lot more manual.
Plus, as has been mentioned, the hypervisor can be as small amount of code as possible thereby reducing the bug and security fronts.
Personally believe that containers are dead. Long live hypervisors!
;-)
Biting the hand that feeds IT
