If you use a native IM client to connect to Google Talk and also have a Google+ account, you probably have noticed by now that your contacts list is polluted by tons of addresses of the form annoyinghash@public.talk.google.com. Attempting to talk to these people from the native IM client does not work (maybe it does in some specific situations? I don't know.), so these contacts only add noise and annoyance.

It turns out that these "spurious" contacts are the people that you have in your Google+ circles, and I suppose allows such people to talk to you when you are logged into Google+. Me, I don't necessarily want to allow all of these people in my chat list.

After a bit of searching around, I have found that it is possible to remove them completely from your Google Talk list. Because all the answers I could find were incomplete and/or vague replies to forum questions, I'm writing the procedure down here for posterity. Do as follows:
  1. Log into your Google+ account.
  2. Sign into the builtin chat client on the right-hand side panel.
  3. Open the drop-down menu next to your name within the chat client and select Privacy settings.
  4. In the Choose who can chat with you option, select Custom.
  5. Unselect all the circle names in the checkboxes that appear.
  6. Click save.
  7. Witness all those useless contacts vanish from your IM clients! (Both native and web based.)