Proxmox and Virtuozzo both primarily operate on containers; Proxmox uses LXC and Virtuozzo uses OpenVZ.

With things like kernel same-page merging, LVM thin storage pools, and memory ballooning, the difference between "containers" and "VMs" is reducing to the point where the main difference is whether there's a software layer emulating the hardware or not.

Docker is the new kid on the block, and a bonfire of billions of VC dollars can create a lot of smoke.