The application demonstrated in this talk is hardly handling about 500 users, but demonstrate some interesting points about scalability that could be almost taken for granted in Cloud hosting services like Amazon. Also a good introduction to Cloud if you are not already on cloud 9.
Listen to the MP3 of the presentation here.
Watch slide 23, the non-RDBMS bonus carefully. If you have read about my previous post on this topic, moving away from RDBMS/Tables, the point comes home pretty convincingly in this presentation.