Network growth is founded on valuable information exchange and social interaction. The less tax per exchange, the more rapid the network can grow once adopted by sufficient users. Once two nodes speak the same language a third node can communicate with either or both enriching the network. But differently systems have varied levels of restricted access.
Virtual identity providers Facebook, Google and Twitter require user authentication and permission to public or semi-private data. I say semi-private because any data once shared exists on third party systems indefinitely. Future data access is controlled by the provider not the user. Google also has public feeds to much of its open data, Buzz being its prominent conversation network and it's designed and built from the ground up on open protocols (pubsubhubbub, etc). Facebook and Twitter defer to restricted API access to realtime updates on their networks, to control and monetize access to user generated content. Google mail has a similar user permission system and page based ad revenue architecture.
Open questions to social web industry leads:
Can one to many broadcast networks be commoditizied or will there always be room for paid or ad driven services?
How will personal generated information be leveraged to generate value for the network provider while still satisfying users?
Complimentary Social Apps
An interesting twist is the convergence of social networks and games along with the evolution of Massive Multiplayer Online Games. There's little doubt that games with mass public appeal can generate enormous revenue by selling virtual goods. Contrast this to subscription games which struggle against members who farm virtual currency, often at the cost of the user experience of other paying players (hacked accounts, rare resource camping). Time whether spent in virtual worlds or working on real world projects, has a way of finding a link to perceived value and real currency.
While queueing up for an instance in World of Warcraft (WoW) with friends before breakfast, a Skype conference provided a complimentary social layer. Even after an overhaul the built in voice chat system for WoW has limited functionality and adoption. Ventrillo, another voice over internet protocol service, is the standard for many MMO players. By breaking up dedicated services, customers win with greater choice. There's vast potential for virtual currency (network equity) exchange between networks.