Check out this post from 'The Wayward WebLog'... it is a good discussion starter for anyone who wants to chat about ORM (object-relational mapping) ...

ObjectSpaces: The Devil is in the Demand

I’ve coined the phrase ‘object span’ to describe the ability to front load a graph-based query with enough information to cherry pick at the best bits of data so data retrieval is optimized to the application.  I’ve even written about that here.  Yet I’ve never felt one hundred percent right about any of it.  Not the span exactly, but the whole concept of systems designed to retrieve segments of a data graph into the client space, with interceptors (or swizzlers) that fault in more segments upon demand.  I’ve come to the conclusion that demand loading is just a terribly bad idea.