Good start - I wasn't aware of the Litmus environment. The Animoto example is great, I love telling that story to people just starting to look into cloud computing.

To add to the large-environment roll call, here are the persistent server counts of some 100% cloud-hosted companies:

- Bizo: 100+ instances (I work here)

- Reddit: 100(?) instances ("256 Virtual CPUs" http://us.pycon.org/2010/conference/schedule/event/148/) - HNer jedberg runs this

- ShareThis: 250 instances (I worked here)

Longest-running instance I've had is at two years and still going strong.