In the real world, people rarely interact with other people, or data, in a hierarchical manner. If they do, they lose time and efficiency.
It's not necessary to have an global view of topology of the data, so long as you know about some of it, and know other people who know the rest. The emerging VO architecture can leverage the peer-to-peer nature of agent based solutions to make the software smarter, more efficient and more responsive to the user. The purpose of an agent is to know what a user wants, even if they don't know themselves. Establishing architectures and building agent based solutions for the VO will flatten the network topology, enabling links between related datasets to form more quickly, and make the resulting network more robust.