Gabe on Nostr: When people inevitably start building on the **other stuff**, is it more likely that ...

When people inevitably start building on the **other stuff**, is it more likely that the applications will be walled off on private relays or some how find a way to filter public relays?

For instance, if someone chooses to develop a nostr based market place, how would they go about insuring that the events in their site aren't flooding note based clients?