In some Ning nets, the creator invited the majority of the members. When subsequent users bring in new members of their own, new clusters form to reflect the viral chain.
Each white dot represents one member of a specific social network on Ning. Each starburst defines the extent and pattern of that member's invitations to new users to networks across the platform.
This viral effect means each Ning member is equal to two new users, compounded daily. That's how Ning has grown from 60,000 networks last June to 230,000 today.