Ads which contain uninitiated audio, gambling, adult material, error messages, and "extreme animation" are explicitly banned. As I have explained before, the problem is not with the networks I have agreements with - it's with the people they are reselling my inventory to. They have no obligation to respect my rules, and will not hesitate to run high-paying (to them) audio ads at a very low cost (because they don't have to reimburse webmasters for what the banners are actually worth). Basically, it's theft. As a result, I get complaints about banners that I'm not getting paid for and which I don't even want running in the first place.
To make matters worse, there are several ad networks involved. When a network shows all of the banners that they have, I define another to be its "default". This creates several different tiers, any of which could be the network that is unfairly reselling their inventory. I have no way of knowing which tier these banners are being served from, allowing each network I contact to legitimately claim innocence.
At some point, I have to decide how much theft I am willing to tolerate and track down, or if I'd rather just eat the cost of terminating a relationship with a network. Unfortunately, as these reports continue coming in, it may be time to make that choice.