One current theory is to use influencers, early in your project. Build credible relationships with contacts who have networks of the right people, not necessarily the most people. Leaderboard systems such as Klout and Empire Avenue can quantify individual social media capabilities and strength. Using these gamified leaderboard systems, companies and nonprofits can build lists of high-scoring voices and target them as influencers.
This infographic was designed for an article in SmartBrief in Social Media (http://smartblogs.com/socialmedia/2011/07/15/the-state-of-influencer-theory-on-the-social-web/) by Jess3 (http://jess3.com/) and Zoetica (http://zoeticamedia.com/), based on my book, Welcome to the Fifth Estate (http://www.amazon.com/dp/0910155860).