Google Plus Circle Followers helps to increase the Social media marketing. If your Business page has a good number of Followers, it make sense that you can spread new/offer/new product or anything in one Post. So that all your Followers/customer/clients in your Google Circle view the post. And not only that they also can +1, comment and share your Post to their circle which build networks. So that your post get multiplied and spread all over. This is the greatest strength of Social media marketing