Example of the size of an operation like WoWhttp://radoff.com/blog/2008/08/22/anatomy-of-an-mmorpg/Server Farms
"How many computers does an MMORPG require? In 2006, Vivendi reported in SEC disclosures that it maintained over 1,900 servers
for WoW. Aside from the software infrastructure, the task of designing and then operating a scalable server farm—with all the security, network and maintenance issues it entails—is a huge job in itself."