Google+ Circles are not YOUR filter, they filter YOU. It would be a mistake to create a circle thinking that it will limit what you read from that circle of friends.
For example, I created a Foodie circle on Google+. The circle is where I post pictures of food and recipes. However, when I look at the Foodie circle stream, it contains posts about anything and everything my friends in that circle have shared publicly, which doesn't necessarily include food.
On the other hand, when I post items to a specific circle, only those people in that circle receive my posts, leaving everybody who is not interested unaware.
PUBLIC is the bane of the whole Circles concept. It completely bypasses Circles and blasts everybody with the same message regardless whether they are interested or not.
As a blogger, my first impulse is to share with the world. It requires some self-restraint to not make all my Google+ posts viewable to the entire world. I suppose I could do the same with Facebook; but, I won't. Whatever.
I'm hoping other Google+ users practice some self-restraint by keeping away from the PUBLIC broadcasts with respect to everything they are doing.
- Google + (mythoughtsideasandramblings.com)
- Google Circles may be why physicians will embrace Google+ (kevinmd.com)
- Google Plus Project at 30 Thousand Feet (ferreemoney.com)
- How Google+ Addressed Useful Network Features (conversationagent.com)