If you are wondering how these rankings are compiled, here is what Wikio says:
The position of a blog in the Wikio ranking depends on the number and weight of the incoming links from other blogs. These links are dynamic, which means that they are backlinks or links found within articles.
Only links found in the RSS feed are included. Blogrolls are not taken into account, and the weight of any given link increases according to how recently it was published. We thus hope to provide a classification that is more representative of the current influence levels of the blogs therein.
Moreover, the weight of a link depends on the linking blog’s position in the Wikio ranking. With our algorithm, the weight of a link from a blog that is more highly ranked is greater than that of a link from a blog that is less well ranked.