It's worth mentioning that Bing ads are even less apparently demarcated. At least with Adwords there's a significant contrast created by the use of the yellow which human eyes are particularly sensitive to. I am looking at a Bing ad right now and I am really struggling to see where the ad ends and the white of the search results begins. Not to mention that Adwords has a "Ads related to {}" text along with an information icon next to that. Bing ads just have a small "Ads" in the top right corner of the ad (away from where the eyeballs are likely to be).