I basically came up with the idea of what's now called IaaS (Infrastructure as as Service), back in 2004 or 2005, I think it was? One problem at the time was the lack of fine-grained access control in vCenter, or this might have even pre-dated vCenter. I don't think I could have given customers console access to only their VMs, and nobody else's, without giving everybody their own vCenter, or even their own host(s).