Dunbar's number is Robin Dunbar's proposed approximate limit to stable human social relationships, perhaps due to brain size.
Presuming that Dunbar's number means that a person also likely only has room for a couple of people able to occupy specific domains.
For example, people may only be able to place trust in so many experts in a specific domain.
Dunbar Hacking is when an entity leverages this against people by replacing vital local resources with manufactured parasocial relationships.