Last week Oracle and Amazon Web Services held a webinar to outline how Oracle works on Amazon's EC2, including database backups to the Cloud.
Running Oracle on EC2 is not too thrilling, though it's likely welcome for many organizations. Oracle database licensing fees are similar to on-premises pricing with no immediate way to leverage an on-demand usage model. Basically, if you want/need to run Oracle in the Cloud you can. But you aren't looking at a huge cost advantage.
More interesting is the ability to run backups to the Cloud and take advantage of Amazon's S3 low-cost storage. Backup and disaster recovery are a notorious enterprise burden and anything that alleviates risk and system administration is a welcome relief.
One could argue that backup is the killer app for the Cloud. The Cloud offers a higher degree of reliability and accessibility than tapes with faster time to recovery. It removes some of the human intervention required for a recovery and overall makes it easier for companies to back things up on a regular basis.