Online community marketing can help a brand in these three ways:
Your online community can actively and effectively feed your sales funnel. You will, of course, need to optimize and track the path, from user joining the community through their transfer to the sales pipeline, to becoming a customer.
Online communities are designed for scaling word of mouth. Viral, shared content, direct messages, invitations to join community, mentions etc all these elements will help you reach new potential clients by using the existing ones that are satisfied and willing to share their experience with others. Your task is to provide them with tools and make this process easy and entertaining.
Online communities are user-driven content machines. This huge amount of user generated content is indexed by search engines and will significantly improve your ranking. Do a quick exercise: assign a dollar value of increased placement or calculate the cost of the traffic from search engines with other methods and you will understand what I am talking about.