ACM Queue has an interview with Phil Smoot, a product unit manager (PUM) in Microsoft’s MSN division.
"In the landscape of today’s megaservices, Hotmail just might be Mount Everest. One of the oldest free Web e-mail services, Hotmail relies on more than 10,000 servers spread around the globe to process billions of e-mail transactions per day. What’s interesting is that despite this enormous amount of traffic, Hotmail relies on less than 100 system administrators to manage it all."
Via Om Malik.