Most social media “listening” systems have a way to evaluate the influence of the various sources in your social media ecosystem. They do that by looking at a variety of factors, such as number of incoming links, number of comments, number of unique commenters, Google Pagerank, etc.
The problem I have with these systems is that an influential person for one company may not be so influential for another. For example, a blogger could score really high on all the above metrics yet only influence other social media pundits. That might be a good influencer for one company, but not for a company who is trying to influence traditional press people or a business audience. They would need a blogger who appeals mostly to those audiences.
Does that mean that the only way to determine influence is to look at those influencers manually?