Displaying advertisement, which is identifiable as such on the result pages of search engines are commonly referred to as “Keyword Advertising“. Displaying advertisement in such a way users perceive them search results is considered to be “Keyword Buying“**.[at least about a year ago; now the wikipedia.org-entry apparently has disappeared]
When reading the references of the four national courts (for a list of the cases, please refer to my Legal-Links Tab) which have asked the ECJ for a preliminary ruling I’ve noticed that the Austrian as well as the Dutch court are actually seeing advertisement displayed above the search results as (Top-Ad) as part of the search results and thus Keyword Buying! So when talking about the likeliness of confusion this is something to be considered.
Still, all four courts agree that advertisement displayed beside the (organic) search results (Side-Ads) are to be seen as advertisement beside the list of search results. None of the references actually deals with a case where the advertisement actually contained a (competitor’s) sign. (Adv-)
** Thiele, RdW 2001, 454; Hüsch, Keyword Advertising und Keyword Buying (2005) 20.