Thanks for your question.

We don't moderate categories currently, so it is in the categories selected by the publisher upon ad unit creation. We expected that publishers should select the right categories in order to generate more sales for advertisers and thus increase their income. Since most advertisers don't reward for sales, it doesn't really work. We are searching for a better solution for ad unit classification. Either get rid of categories, or simplify the hierarchy and classify ad units ourselves, or do it automatically. If you have ideas of how to do it better, please let us know.

Thanks!