ken_b - 9:24 pm on Sep 20, 2011 (gmt 0)

From todays Inside AdSense email.

Starting in October, the +1 button will begin to appear on display ads on your site.

Although you won’t receive any revenue for +1 button clicks, ...

If you’d prefer not to allow the use of +1 features and social annotations on display ads on your pages, you can opt out starting today by signing in to your account at google.com/adsense.