When Elastra announced their service to host MySQL and PostgreSQL in the Amazon S3/EC2 cloud, I immediately told my dear darling clients at EnterpriseDB they should do the same. Whereupon they told me it would happen soon. However, they neglected to tell me when it was actually announced. So I know no more than can be found in this Computerworld article.
But I’ll say this — it’s a very tempting option, both for new web-based applications or businesses, or simply as a development platform pending later redeployment.