1. Two entity EJBs are identical if the "equals()" method of their primary key class returns true.
2. Except during method invocation, all instances of a stateless bean are equivalent, allowing the
EJB container to assign an instance to any client.
3. Two stateful session beans are identical if their session contexts are equal, not their data attributes. Multiple clients can not get the same EJB by "creating" new stateful session beans and setting their data attributes to the same values.
http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/Session3.html#63661