Symmetry vs. Asymmetry in Social Networks

Re: http://bokardo.com/archives/relationship-symmetry-in-social-networks-why-facebook-will-go-fully-asymmetric/

Twitter is asymmetric. while Facebook is symmetric (and Linkedin, too). This, I learn form the author Joshua Porter, is probably the reason for the steep growing curve of Twitter in the last few months. I agree, relationships symmetrically defined involve only a simplistic world of friends, while asymmetric relationships allow for a more complex network - like in “real world”.