Ross Mayfield puts forward an analysis of online social networking models that covers explicit, physical, conversational and private online networking
The differences of these Social Network Models will trend to blur, but each example possesses a unique and dominant connection method. Ryze facilitates physical meetings (in fact that’s how the community began). Weblogs and LiveJournal do not emphasize identity like Ryze, but share their own differences. Weblogs are decentralized while LiveJournal is centralized and does emphasize ties, which explains the denser clustering of relationships. Friendster increasingly provides mechanisms for making identity explicit. But each model has a unique and dominant property for social networking. Pointing out these distinctions isn’t a call for Social Software builders to emulate each other. People don’t just join one community, they join many, and they appreciate diversity and choice.
Ross also posts about the use of collaborative ratings systems in social software as a currency or measure of trust.