Google announced on one of their blogs that their AdSense network will be getting +1 buttons on display ads. So not only can users “endorse” products or services by clicking on a +1 button, but it will cause the ads appear more often to their social connections, hopefully making for more relevant ad targeting.
Starting in October, the +1 button will begin to appear on display ads on your site. With a single click, people will now be able to endorse specific ads and make them more likely to appear to their social connections. We believe that these recommendations could lead your readers to notice ads on your site more, leading to more clicks and higher returns for you over time.
Clicks on the +1 button will not count as ad clicks, and publishers will not receive revenue for them, but should help increase CTR. (People are more inclined to click ads that are recommended by people they know.)
+1: Now making Display ads more relevant [Inside Adsense Blog]