Earlier, Google launched +1 button on Google search and for publisher sites to make it easier for readers and users to share and discover content across the web. Adsense will introduce the +1 button and personal recommendations to display ads from next month onwards. As a result, the +1 button will begin to appear on AdSense for Content and AdSense for Mobile Content display ad formats .
Why +1 in Adsense
In order to assure the relevancy of the ad, +1s will determine with greatest role. This will result in generating the most revenue for an Adsense publisher. A lot more coming for Adsense publishers, in which your users will be able to endorse specific ads and make the ads more likely to appear to their social connections. These suggestions could help your readers notice ads and thereby increasing the chance of getting a higher revenue.
What if I don't want +1 button
Simply opt out displaying +1 button from your account.
But remember, More relevant ad display means more income.