[machine-wisdom]

Non-relational DBs (the Not Only SQL sort) usually passes the buck up to the application layer for several things. It is in a way a good thing to do if the DB wants to focus on scale out issues such as consistency of replicas or high availability. I personally find it pretty easy to work with alternate data models, thus not relying on the possibility of a join or a transaction, as long as I am not writing a banking application. Without a relational data model, the biggest problem becomes verification IMHO; verification of the DB, the application logic, and whether the application logic makes the right assumptions about the DB it is using.