Determining why a VMware virtual machine was powered off or restarted

Who did restart or poweroff my virtual machine? As an ESX admin this could be a question from one of your VM admins. The following artice describes how to find the issuer and the method behind such an event.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1019064