Wish I had an answer for you, but I'm afraid Google is using less than ideal methods to try to grow their network without providing an alternative.
If you don't mind me piggybacking on your Google+ question with a similar annoyance that I'm dealing with - I made the mistake of joining/adding the HackerNews Google+ circle that somebody here had created awhile back. Now my chat client (Trillian) thinks I've got over 700 Google Talk friends that I want to keep in touch with - these are people I don't know and will never chat with. I've tried re-installing Trillian, and deleting these "contacts" from Trillian, but they keep coming back. I've removed myself from the Google+ HN circle almost immediately. These people don't show up in my Contacts list in GMail. Anybody have suggestions on how I can get rid of them?
If you click the options arrow on the chat feed (next to your name/status), there is a "Privacy Settings" option that allows you to specify which circles can chat with you.
fwiw, you can also specify which circles are in "Your circles" (the ones you broadcast to) and which circles you are just following in the G+ settings (https://www.google.com/settings/plus).
If you don't mind me piggybacking on your Google+ question with a similar annoyance that I'm dealing with - I made the mistake of joining/adding the HackerNews Google+ circle that somebody here had created awhile back. Now my chat client (Trillian) thinks I've got over 700 Google Talk friends that I want to keep in touch with - these are people I don't know and will never chat with. I've tried re-installing Trillian, and deleting these "contacts" from Trillian, but they keep coming back. I've removed myself from the Google+ HN circle almost immediately. These people don't show up in my Contacts list in GMail. Anybody have suggestions on how I can get rid of them?