While I agree with him on a lot of things, this isn't one of them; security is all about layers, and it's not like OpenBSD hasn't steered clear of other forms of sandboxing (like chroots and systrace). This doesn't mean that virtualization should be relied on exclusively or even near-exclusively as a defense (which is what I suspect Theo was more objecting to, along with the point of "well if you can't write a secure operating system, what makes you think you can write a secure hypervisor?"), but rather that it should be used as an additional layer on top of (or rather, underneath) a bunch of others.

It's like bulkheads on modern ships. Yeah, if you get a hole in your hull, you're gonna be in some (literally) deep water, but that bulkhead (so long as it's built right) could mean the difference between limping to the nearest harbor or sinking to the nearest seafloor.

Or you could have a consistent repeatable way of doing it across multiple apps and operating systems. I am not averse to your argument that doing it at the app level has benefits, but being able to do it at the VM level in a consistent way is going to be simpler when you expand beyond a handful of applications.

KVM, VMware, and Xen all allow you to do a snapshot of memory as well as of disk. It's one of the tools used to migrate xen instances between nodes, for example.