Aaron Wall, author of SEOBook and seobook.com posted an article today calling Chitika the “5th search engine” and offered the following observation:
They have been aggressively signing up bloggers and other independent publishers, and are now getting over 2 billion monthly impressions, with their behaviorally targeted Premium ads getting hundreds of millions of monthly search driven impressions, putting their search distribution network on par with Ask.com. 
Click here to read the rest of the article.