Klout: You can not measure online influence -
... but you can certainly find better indications for it than the number of followers on Twitter or friends of Facebook -
Klout is attempting to do the same thing in social media, as Google did 10 years ago for search: measuring indicators of quality & importance, which are not easy to manipulate. For Google, it was mainly about the "linking in": you can fill your web site with keywords, in order to be ranked high - but its much more difficult to get other pages to link to your page.
Klout doesnt simply measure, how many people follow you, but rather, how many ACTIVE people follow, how many times you are mentioned, how many re-tweets, comments you get etc.