John,
I do think that EntityBeans can be used in the situation of the case study. If you look at the Customer Component Diagram you can see that the CustomerDAO does not use any subsystem to persist the account information.
Problem however is that the account information is aggregated from Customer, Address and CreditCard object(s). To solve this you can use the Composite Entity design
pattern (see
http://java.sun.com/blueprints/patterns/CompositeEntity.html). While I think that with
EJB 2.0 this is a good solution (using CMP and CMR), with EJB 1.1 this solution involves quit a lot of coding.
I think that Mark Cade with EJB 1.1 in mind chose for the simplest (thus best) solution, but with EJB 2.0 EntityBeans are a viable solution.
Edward Peters