Klout generates this list by semantically analyzing the content you create and the resulting responses. Your most influential topics are not those topics you talk about the most, but those that you get the most engagement on. If someone has influenced you on a topic you can give them +K on their Topics page. If one of your topics doesn't feel right to you you can remove it in your own topics tab.
Learn more: http://corp.klout.com/blog/2010/07/influence-is-all-about-context/