While designing a virtual infrastructure you have to consider a lot of options: Are we going for ’normal’ server or do we use blades, are we going for an iSCSI SAN or are we going for a FC SAN, etc.
If you got your infrastructure divided over a couple of locations you got even more things to consider like one or more VirtualCenter servers, centralizing servers or placing ESX Hosts on decentral locations.
VMware has a very nice article on the design considerations of ESX hosts over WAN connections with VIrtualCenter.
quote from the site:
Many VMware customers have virtualized their ROBO (Remote Office Branch Office) offices in order to reap the benefits provided by VMware Infrastructure such as hardware cost savings, business continuity and high availability, and lower maintenance costs. Because of ROI considerations and the desire to keep management of ESX hosts and virtual machines centralized, many of these customers choose to keep one VirtualCenter server and configure it to manage ESX hosts over the WAN.