Self-regulating social networks

The basic idea behind social networks such as LinkedIn or MySpace is that you have a set of registered users you are connected to, but the influence this has on the kind of resources you get recommended is almost non-existent. The most I could think of right know is that your connections to other members are exploited for collaborative filtering. What is missing is some kind of social network model which is able to express the kind of connection that you have to someone else - let's say, someone that is working on exactly the same problem as you are, another person that you usually go jogging with, maybe a third person that you share your love for music with, and the like. It would not be much effort to specify the kind of connection to a person when you ask them to be added to your list, but the requirement I would have is that this relation will adapt itself in conformance to the interactions with the system where you have your social network. In that case, I imagine it would be really fun discovering new people that otherwise you would never have met, or get recommended really useful resources to look at.