Virtualization per-se in a Linux environment has only marginal benefits. Many of those benefits can already be achieved in other ways, and it looks like from examining the road maps for Linux Kernel development that most, if not all, of those features will be available for Linux-on-Linux 'virtualization' in the near term.

I'd go so far as to say it is going to be pretty hard to even draw a line and say 'this setup is virtualized' and 'this setup isn't'. You COULD draw the line at a 'container' maintaining its own supervisor level address space, but frankly if the host and guest are the same OS what exactly is the advantage of that in the 1st place? It really isn't much different than running some microkernel based architecture. Worse really.