"SQL Server Data Services (SSDS) are highly scalable, on-demand data storage and query processing utility services. Built on robust SQL Server database and Windows Server technologies, these services provide high availability, security and support standards-based web interfaces for easy programming and quick provisioning."
There is also a nice blurb from Greg Reinacker:
"We at NewsGator are excited about SQL Server Data Services; Microsoft is clearly thinking through not only the product functionality (such as advanced query capabilities), but is also committed to providing a service with the appropriate SLA and uptime characteristics we need to leverage it in our online platform and applications. As soon as they’re ready, we’re planning to store many terabytes of content on this hosted service."
—Greg Reinacker, Founder & CTO NewsGator Technologies