Now I'm back again; Jimmy, that is. It's time to summarize the style variations just described by Mats, Frans, and Ingo. Which one is best? It depends! Life is full of tradeoffs! Would you like to hear some more very good and useful nuggets? What is good and what is bad about the different styles? Here's another good nugget: Make your own decisions, for your own specific situations.
I'm sure you got my point here. As you understand, I didn't ask my friends to write some about their ideas on the subject to see which approach is best. I asked them write about this problem to get you some exposure to other points of view and some inspiration from other styles.
If I were to write micro-summaries of their styles, I would express it like this. In Mats' case, I believe the title is a great summary, namely "Object-Oriented Data Model, Smart Service Layer, and Documents." Mats is fond of locating the behavior in the Service Layer and seeing the Domain Model as an object-oriented representation of the data. "Documents" is about the exchange format between different tiers.
Frans stresses the importance of using the power of the database and that the representation in the database is the true one.
Ingo talks about the importance of finding the right abstractions and that you shouldn't expect to be able to use a single standard style for all situations. Add to that a big chunk of pragmatism.