Nice seo video about keyword density and double se listing
 

Example was on made on mainstream store with various items,but i think this could used be on adult as well,especialy for sites who have general and multiple content.
Video have 22 minutes so dont click on it unless you plan to view it entirely.
http://www.freeinternetmarketingcour...atural-videos/

thx, very interesting :-)

Thanks for the link!