Of course. My point is how to keep it from becoming one in the first place.
Currently all clients send all notes to all your relays by default. Editing your settings manually to disable all other relays is bad UX so of course people will forget or not understand they have to do it.
So even with a trust system you need something on the client side to direct certain notes only to specific relays.
Either this can be a different event code or an option in the client to specify on the note creation screen if you want it to go to all relays or just a specific one or group.
But either way you need some level of automation if you only want specific content on a relay.
I guess the other alternative would be tell everyone they must make a new key. Most clients use different relay lists for different accounts. But even this behaviour isn't universal.