Google AdSense team has intimated that wef next month, they will introduce the +1 button and personal recommendations to display ads. The +1 button will begin to appear on AdSense for Content and AdSense for Mobile Content display ad formats -- image, animated gif, and Flash. +1s will be one additional signal to help determine an ad's relevance and we'll continue to show the ads that will generate the most revenue for you.
Google previously launched the +1 button on Google search and for publisher sites to make it easier for people to share and discover content across the web. This feature is helping the users to endorse specific ads and make the ads more likely to appear to their social connections. Google believe that these recommendations could help your readers notice ads on your site more, leading to higher returns for you over time.
Google says that if one prefer not to show the +1 buttons on display ads on their pages, they can opt out in their account. For more information one can visit the Inside AdSense blog.