Recently, the web has been a-twitter about the partnership between Klout and Audi on Facebook. This article points out - accurately - that there are some limitations to the services as currently providing.
Profile Limitations: Based primarily on activity within Facebook and Twitter profiles, these programs have a good basis upon which to measure social influence. But they lack the influence of bloggers, key industry professionals on LinkedIn, new technology lovers who place their emphasis on sites like Tumblr, or those with influence in real life who do not use social media as a primary form of communication.
Lack of Sentiment: In digital PR, sentiment analysis is a crucial component of success. And we know that the technology for sentiment analysis exists. So why do our "influence identifier" programs lack this functionality? It would seem to me that an influencer who is primarily known to receive negative feedback might now always be the best person to use for outreach efforts for your brand.
Timeliness: I'm torn between whether I'm a fan of this functionality or not. The way it currently stands, taking a break from the digital world can lower your influence score. I feel that the solution to this is to use an algorithm that conducts a cross-analysis of a few different time frames to determine an average of influence. No one is on the top of their game 100% of the time.
Takeaway: Measuring social influence offers a great opportunity to reach out to the key people who will effectively increase exposure for your product, service, or brand. Just be aware that limitations exist for this science, and you need to make sure you use this information with some caution.