Google is now bringing the +1 button to AdSense and display ads within the Google ad network. You will start to see the +1 button on these ads in October.
Google said, "+1's will be one additional signal that help determine an ad’s relevance." Not only that, if a friend of yours +1'ed an ad, they will see their friend's face on the ad and maybe, the ad will more likely show up for your friends.
Here is a picture:
Pamela Parker has a deeper look at this at Search Engine Land where she has a nice quote from Google:
"When an ad is personally annotated, there's a positive impact on click-through rate," Christian Oestlien, Lead Product Manager for Social Advertising, told me. "You get this great win of users becoming advocates for your product...you can take advantage of social and you don't need to come up with new metrics. All of this is baked into all of your existing ad campaigns."
You can block these from showing on ads, if you like.
There is a detailed help document on the details of this over here.
Some folks at WebmasterWorld are calling this as if Google is crossing over the "creepy line again."
Forum discussion at WebmasterWorld.