There is an interesting interview with Werner Vogels which is partly about how Amazon does Service Oriented Architecture:

For us service orientation means encapsulating the data with the business logic that operates on the data, with the only access through a published service interface. No direct database access is allowed from outside the service, and there’s no data sharing among the services.

I do not understand that. Why do they need to 'wrap' a database into some layer if it already can be consumed as a service by other service through database adaptors? Does Amazon do that just because they need to expose the database to third parties or because of anything else?

Why "no direct database access is allowed"? What are the advantages of such an architectural decision?