Patterns for building social network type applications?

Question

I need to design / architect / develop a web based social network type application.

Basic functionality:
- users create accounts on the system
- users agree to

Answer 1

a Graph Database like http://www.neo4j.org is a choice to look at. It lends itself very well to both the social network (e.g. http://blog.neo4j.org/2009/09/social-networks-in-database-using-graph.html) and the ACL-based security (e.g. http://wiki.neo4j.org/content/ACL ).