Why put a DAO layer over a persistence layer (like JDO or Hibernate)

Question

Data Access Objects (DAOs) are a common design pattern, and recommended by Sun. But the earliest examples of Java DAOs interacted directly with relational databases -- they were

Answer 1

I suppose that the pattern "DAO class per entity" is absolutely redundant for an ORM-managed data layer. Instead, the DAO layer should be composed of a set of one-fits-all CRUD method set that operate on arbitrary entity classes and a large number of methods that perform more sophisticated operations on data. If the functionality is large enough then the DAO layer should be split into multiple classes based on the domain criteria, what makes the approach more similar to the Service-Oriented Architecture.