Klout.com aims to help you understand your social influence. Currently the site analyzes data from your Facebook, LinkedIn and Twitter accounts. Personally I use LinkedIn to manage my career and keep in touch with business contacts whereas I use Facebook strictly to keep up with friends and family.
While I used Twitter for a while, other then letting people what I am up to on Blogger, I find it pretty useless.
Currently my Klout reach is 11 of 100, I wonder how they calculate the score?