I love Google Plus, and it's been great for my business. I know there's a core group from here using it religiously and using it very well. There are also several here that dabble in it.
For those that dabble, I see this common mistake...and it REALLY ANNOYS regular google plus users...and many will uncircle you if you do this repeatedly.
When you post your update, DO NOT select "notify your circles." And, related, make sure you post to public. If you select a circle and/or notify your circles, they get an alert about your post. And, most see this as spam. Many will report you; others will unfollow you; others will mute you. And, you have no way of knowing. But, basically, you have been spamming your followers and annoying them...even those that are still following you.
I've seen so many posts and comments about this. It's equivalent to writing a blog post on here and then emailing all of your subscribers to check out your post. That is not the way it's supposed to work. Instead, people to read the stream and choose what they read/view...similar to what I do on Active Rain. I will go to my subscriber list when I'm ready and/or go to the feature page and/or toggle back and forth. I control what I see. Getting the notification about a new update is interuptive and annoying.
Now, once in a while, you may have a very important post that you want to share. I would venture to say that this may be one in every 100, if that. Also, if there are specific people that you want input from, then mention them in the post by typing +their name (no spaces). That way, they get a mention, they are notified and it helps their google authorship.
So, the takeway? Just post to public and do not select the option to notify your circles.