Linux Containers, which docker makes use of, are more like creating a "clone" of the currently running operating system with a boxed-in filesystem (and device-space?).
You can't run a Windows container on a Linux host; neither can you run a Solaris container on a Linux host; ad nausium.
With VMs, you can run whatever you want on whatever you want, assuming the processor architecture is compatible.
This is not accurate. I am currently running an Ubuntu Docker host, but a CentOS 6.4 based container, a Gentoo container, and a busybox container.
As stated elsewhere in this thread, which I encourage you to read, Docker aims to solve problems that exist in container technologies across kernels by taking advantage of their strengths (Docker does not aim to replace libvirt/lxc/jails/zones) but instead to build abstractions on top of them for better building, management, discovery, and scale.
In your "counter-example", you're running four different userspaces/distributions on the same operating system kernel.
You could have posted a useful clarification to my comment (e.g. "but you _can_ run different Linux distributions!") but instead have chosen to be condescending and inaccurate.
My only comment was in response to 'creating a "clone" of the currently running operating system.' Which is not, in any sense, accurate.
What is shared, as you correctly point out (and I do not refute) is that kernel and devices are not virtualized per container. So you're absolutely right, it's not like a VM. And it does break down, but none of that has to do with the part where your statement is incorrect, which I've addressed and expanded upon.