Amazon provides AWS with problems to solve that are going to be general problems to solve in 2-3 years. Amazon developed DynamoDB and S3 and handed them off to AWS to operate, for instance.

Without Amazon's innovation funnel, AWS will be Rackspace in 10 years (well, maybe Oracle in 5 years). Maybe they'd keep adding more hosted services (Announcing ClickTower, our columnar database as a service!) but that's not innovation.