@ConfusedAboutDAGActive/ActiveHA - If there is a concern about maintaining service when WAN connectivity is lost between datacenters, then the only solution is to place the FSW in a third site. I didn't want to bog this article down in those intricacies since it is not directly tied to namespace planning.
@Petri X - Yes, we recommend multi-role deployments. These examples just highlight the specific function each role has, and does not imply we recommend dedicated role deployments. Yes the unbound model can have more than 1 DAG - I used 1 to highlight the differences between unbounded and bounded; obviously, if you have more mailboxes or servers that can be instantiated in a single DAG, you will need to create more. However, the difference between unbounded and bounded still exists - one is used to control connectivity, while the other is not.
Ross