Google has finally enabled instant messaging with your contacts on Google Plus on Talk.
Until now, you need to know the email address of the other person to add them on Google Talk.
Google Talk now supports conversing with anyone who is mutually connected to you on Google Plus.
This is important because you can connect with other people without revealing your email address on Plus.
Google Chat makes it easy to chat with people you have relationships with. In Google+, you can chat with anyone in your Circles who also has added you to their Circles. And, when you’re not using Google Plus, you’ll still be able to chat with them using Google products including, Gmail, the Google Talk client, iGoogle, Orkut and 3rd party apps.