Have you ever started typing an email to someone only to realize halfway through the draft that you haven't actually exchanged email addresses? If you are nodding your head 'yes' and already have a Google+ profile, then you’re in luck, because now it's easier for people using Gmail and Google+ to connect over email. As an extension of some earlier improvements that keep Gmail contacts automatically up to date using Google+, Gmail will suggest your Google+ connections as recipients when you are composing a new email
Your email address isn't visible to a Google+ connection unless you send that person an email, and likewise, that person’s email address isn’t visible to you unless they send you an email.
i don't use or even add anyone to my Google+ account so i don't think this will affect me
Sligthly off topic I once started to register a facebook account,from my ipad, not my main computer,even before I had completed it "Facebook" suggest a few people I might like as friends,the thing was I new all of them,even as far away as Australia and Japan,
I can only think it had cross referenced email addresses from my main computer and then matched with facebook accounts.