An aspect of object oriented programming that is simpler to do with an object relational mapper is lazy loading one object type from within another.  For example, if we want to load up the Owner object of an Event object, for instance, the company hosting the event, we can write our lazy load property in the Event object and then simply create an Owner object with the owner id key returned from our Event object load.  In this way your object model can grow and objects maintain a high level of encapsulation.