Justin Briggs illustrates how search engine users pay attention to search results that include video thumbnails in his excellent post, How Does Google Authorship Impact CTR?
I pulled the following quote from his blog to put the accompanying heatmap in context:
“…the social annotation is pulling a user’s eye down the page. In this case, the vertical distance from the top of the page to the annotation is significant. It still draws more attention than both highly visual video search results.” Read the rest at Justin Briggs.