I do not see why Yahoo would ban someone who is doing well and making them money as long as the clicks and traffic are honest. They must have detected something on your site. I agree; they can be less than accommodating when you need help and once they decide you have committed an infraction, you probably become person non grata, which is not fair. You should be able to defend yourself. On the other hand, they have the compliance manager which gives you a chance to fix mistakes you are making before being booted. It's more than AdSense does.