If you share via email, and you check the "Also email x person/s not yet using Google+", it will email those people your post with an invite to join as well. I

If you share via email, and you check the "Also email x person/s not yet using Google+", it will email those people your post with an invite to join as well. I actually don't mind this because it lets me share my thoughts with people that have no interest in G+ without having to do it twice.