Initially the great idea about Google+ Circles is that it made it easier to communicate to the many people in our circles, we were excited about that we could choose who our message went to, and we could select who we wanted to listen to. Awesome!
However, as our circles grow (and generally we want our circles to grow) we now want our circles to plant themselves. We complain about the noise, we complain about the limits that Google+ places on followers.
In order for Google+ to grow we need a way for people to directly join our specific circles. As we seen on Twitter and Facebook circles/followers/Fans/etc. can grow easily into the thousands. It’s too much to expect the individual to cultivate so many people. Without this feature, I really think Google+ will stall.
Frankly, I’m surprised that Google didn’t foresee this. A set of public vs private circles seems to be the answer.