Speakers from JPL at the Amazon Re:Invent conference just described how they used Amazon Web Services to provide real time video and images to the millions of people watching the Mars Rover landing. This is a perfect example of how the cloud can scale instantly to meet demand. JPL watched demand grow as the landing neared and added more cloud capacity instantly with a couple of clicks. At one point, traditional JPL servers melted down under the load and they re-routed everything to the Amazon cloud instantly, which handled the load with no problem.
Cloud computing is metered, you only pay for what you need, with no minimum fees. It scales instantly and lets users concentrate on building applications while Amazon handles the infrastructure and network. Other major cloud vendors include Microsoft and Rackspace (which this blog runs on via Laughing Squid.)