Keep Others From Sharing Your Circle Posts on Google+
Here's how to disable sharing private conversations on Google+
At least so far, Google+ in beta defaults to a setting you probably don't want for your posts. Currently, if you post something to a specific person or Circle, anyone who sees the post is able to share it in his or her own Circles. So change that default setting. Here's how./p>
After you write your message, decide which users or Circles to share it with. Click Share.
After you share, click the dropdown menu at right and select Disable Reshare.
This way, your contacts won't be able to reshare the message you sent to them. A wise thing, for sure.