On the 18th April 2013 Google announced that they have made a Google Plus commenting system which you can have on your website just like the Facebook comments. This allows people to come to your site and when they comment on an article this comment will be shared on Google plus.
Demo: Google+ Comment Box
For now, it is available only for blogs on the Blogger platform. But here is an unofficial way to embed Google+ Comments on any Simple Machines Forum:
// Maybe they want to report this post to the moderator(s)?
if ($message['id'] == $context['topic_first_message'])
Official Blog: Bringing Google+ Comments to Blogger