itworked - 2:48 pm on Aug 23, 2012 (gmt 0)
Nummum I'm curious as to whether you have done any testing on this over the months since your original post.
One reason category blocking might reduce revenue overall is that there is not an unlimited amount of ad inventory. There are only so many ads per ad type, ad size, etc. and if the ads are contextual, that limits things a bit further.
So I would speculate that "under-performing" category blocking given your original definition of under-performing would increase revenue with two caveats. 1) there is an unlimited supply of potential ads 2) you are not blocking categories that have a strong contextual connection to content on your site.