+K is a personal endorsement of people in topics they are influential on
Klout is a tool and indicator that measures the influence of users on Twitter, Facebook and LinkedIn Social Networks. Klout recently announced the +K, a new feature that enables Klout users to endorse their friends who have recently influenced them on certain topics that they discuss on Twitter or Facebook.
Klout is measuring your social media influence on LinkedIn as well
Klout is a web-based service that measures the influence of social media users. Until now, the Klout Score was based on your influence on Twitter and Facebook. Now you can add LinkedIn to Klout, and your influence on the network will also be added to your score.
+K is the ability to endorse your influencer in a topic
Klout is a web-based service that measures the degree to which one is influential or has clout on the social media like Twitter and Facebook. Klout introduced the +K feature which lets you vote for a user on Twitter or Facebook who has recently influenced you in a topic.