It would be nice if google+ extended the circle metaphor to include public circles, that people can discover and join, giving us a way to easily make and follow channels with a narrow subject on Google+
What this would solve is the following basic problem:
I don't want to hear mumbles on random topics, from people I follow for one subject in particular. For example, if I follow you for your technology knowledge and opinion, I dont want to hear about the food you're eating on your latest visit to china.
I should be able to join your technology circle, provided you've made it public, and by so doing I should be able to see only the posts you send to your technology circle.