Yes, I completely agree. @bstrong & @Vilen have taken this on and we think it's really important. The question is how to design it to be simple enough for everyday consumers to use. My understanding is power users liked the concept of Circles at G+ but there was too much friction for consumers.
Also, we want to make sure we construct it so it will scale from an engineering point of view so we don't tip over at scale like Twitter and Friendster did.