friendship models

I implemented a friendship model like Flickr's where you can have a
friend that doesn't call you a friend... I used Josh Susser's
self-referential model
(http://blog.hasmanythrough.com/articles/2006/04/21/self-referential-through).

I want to change to the myspace model where two people are either both
friends, or not at all.

Are there any examples out there that implement it this way?