At IDF 2010 in SF, we had the opportunity to demonstrate a nice use  case for HPC in the Cloud – when you have tapped out your local cluster  resources, provision your excess work to the Cloud. 10GbE iWARP was used  for the local cluster as the performant low-latency fabric.  Mainstream  10GbE was used in the Cloud as it provides the dynamic virtualization  and unified networking features required for virtual data centers.  See  the class I presented on HPC in the Cloud networking - it covers some  additional usage models and some key features required for cloud networking.