The way Google+ Circles works is a differentiator from how other social networks (say, Facebook) organize a user's contacts.
It also just got easier to do.
Google has tweaked the Circles page-design, adding a left-hand navigation menu -- making it easier to get to email address books. The icons also scale better for small screens.
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A larger improvement is a more robust search. Users can find people and brands they have an interest in, with a list of related suggestions from Google that the user may want also to add to their Circles.
Google is working on new algorithims "to match users based on friend connections and interests," according to The Next Web.
Given Google's immense amount of marketing, sales and advertising -- as well as user behavior and impressions -- these tweaks could lead down a quite robust and lucrative path.