One of the long standing issues with social networks and social community sites if the ability to have portable reputation and identity specifically if you are a good upstanding member of the community. Here is a very good Lifehacker article on openid and the promise of what it brings as well as some of the concerns surrounding the system, or set of systems.
I know that Marc Canter has been addressing some of these issues on his Broadband Mechanics blog and the people aggregator program. Reputation transfer has always been a confounding issue. One of the reasons is that every network is built with a unique system. The Open ID does not transfer data and information between networks but does maintain an identity. Not only does it allow of an approaching universal single sign on, but it maintains displayed identity throughout the gamut of spaces that you visit.