Anyways, like I said, last when I spoke to Ed was about pushing the virtualization security initiative here in the EMEA. I have spoken to several little and bigger players, including our own large team ("our" as in my employer) of some 500+ security experts,who are doing lots RA's for firms across the globe.
Anyways here's Haletky's article:
The roles and permissions within the VI Client do not necessarily map to users and groups within the service console or management appliance. Roles and permissions are quite a bit different actually and do not always map one to one.
When you directly connect the VI Client to a VMware ESX or VMware ESXi host you will use a local username and password to log in. But after that, all actions depend on your roles and permissions within the VI Client. The VI Client does not run any command as the user to which you logged in. Instead it runs those commands you are entitled to run as the root user. Since the root user is also the super user, it can run any command available to the system. This translation happens automatically as the vmware-hostd daemon runs as the root user.
The same happens when you log in using the VI Client to VMware vCenter Server. VMware vCenter Server uses the vpxuser to contact the vmware-hostd daemon which in turn runs all the necessary commands as the root user.
For a direct connection, a user must exist on the VMware ESX or VMware ESXi host, but for an indirect connection, no user must exist on the hosts. This implies that when you use vCenter there is no real need to manage multiple user account systems. Unfortunately, in reality you often have to have users on your VMware ESX and VMware ESXi hosts to perform support actions.