Virtualizing High Performance Computing

There have been a recent set of VMware Communities questions that have got me thinking about the prospect of virtualizing high performance computing (vHPC) and whether or not this is even practical, reasonable, and would give any gains to HPC. I think there are some gains to be made but with everything there are some concerns as well. This is of interest to me as at one time I was deep into High Performance Technical Computing and marrying Virtualization to HPC/HPTC would be a very interesting option.