I do not see PPC ads when I search on bing. I cannot figure out why. I tried Vista/IE8, XP/IE7. No ads 99% of the time.
Not sure if this is what your post is about.
Anyone have a guess as to why? I contacted MSN Adcenter support and they had me try basic things like clearning browsing history, cookies, resetting pop up blockers and security settings. Nothing worked.