Well-established strategies that people can expect smart relays to implement. DVMs that can perform aggregation/analysis/discovery on relays, including AUTH-protected ones. Clients that can use smart relays. Conventions for using different relays differently. Lots of things, mostly based on establishing good conventions and a shared mental model for this stuff.
DVM is definitely something we want to build.
We were also thinking of setting up a page (at a .bit domain controlled by the client) that would act as the canonical source of information for the .bit name holder so that clients can be guarantied to receive every note the people they follow have ever posted (or at least the ones they want them to see). An added benefit is that it seems that clients would be able to pull information faster with such an architecture.