It seems to me that Demand Media is the realization of the original dream of "The Mining Company" (later became About.com). They've created an efficient marketp

It seems to me that Demand Media is the realization of the original dream of "The Mining Company" (later became About.com). They've created an efficient marketplace for generating content in direct response to user's search queries. But how does content specifically designed to answer a question, make more money showing contextual ads than it costs to produce the content in the first place? If the content is answering the query, what ads are users clicking after reading it?