I have a hard time getting upset about banning negative banner ads on Yahoo. I think that moreso then on TV, ads do reflect on the site carrying them, as there is less seperation between ad and content. This lack of seperation causes problems as advertisers abuse this fact to trick people into clicking on ads that look like operating system messages or even a normal part of the site they are viewing. Forcing Yahoo and friends to carry negative banners would directly impact the public perception of the carriers and I can't force them to do that.