Google launched the new instant previews in early November. Since then, we have seen it cause some serious damage in Google Analytics, but now I see reports of people claiming it is damaging their AdSense ads.
A WebmasterWorld thread has one person claiming he sees some AdSense ads being displayed in the Google Instant previews. If they are, it may mean that those ads are being fetched and counted on some cases when someone mouses over a search result as opposed to clicking on it.
I tested it out by searching for my personal blog, [cartoon barry] and my AdSense ads are being blanked out. Here is a picture:
Sadly, I just don't have time to spot check this on other sites right now. But this guy claims he sees AdSense ads in some previews. He is a member of WebmasterWorld since 2004 and someone else said he saw them too. Have you? Should we be worried? I am sure publishers don't mind the extra impressions but what about advertisers?
Forum discussion at WebmasterWorld.
Update: So the Kosher Food Reviews site has AdSense displayed in the preview. Here is a picture:
Update 2: I forgot, as Googler, JohnMu commented: