In every network, people cluster by affiliations. These are affiliations based on shared transactions, ideologies, interests, adversaries, demographics, and histories.
And there are two basic types of affiliations, dynamic and static. In static affiliations, people cluster with an intention to protect the membership and characteristics of their affiliation. Sociology sometimes refers to these as "strong cliques" where people feel a relatively strong/sticky sense of loyalty to one another and the basis for their affiliations.
In dynamic affiliations, people cluster with an intention to grow and evolve their cluster's membership and characteristics. They are more loyal to the kind of inclusion and diversity that allows the cluster to emerge as a self-organizing, adaptive ecology of connections.
When it comes to growing networks, one strategy is to grow more dynamic clusters of collaborations and transactions. Another strategy is to expand weak static affiliations that may not be as attached to their clusters' status quo.