Iceberg Sources

A question regarding long-term reporting projects.

With as many interviews as you're likely to do, you probably can't (or shouldn't) quote everyone.

So is there a good way to tell the person who just gave you an hour of their time that they probably won't appear in the story?

Should you inform them of that possibility beforehand?

These days especially, certain people give interviews about someone else or something else specifically because they want publicity for themselves.

Is it our job to let them know they might not get it?