Great example of scalability on Windows Azure, from 0 to more than a million users

During the recent spring release of Windows Azure a session was streamed about an application that needed to grow rapidly from no users to more than a million users in a short period of time. Have a
look at https://www.meetwindowsazure.com/Conversations#Pottermore to see the capabilities for scalability that Windows Azure can offer along with Sharded SQL Azure (approximately 500 shards)