How Will Google Plus Affect SEO? http://www.readwriteweb.com/biz/2011/07/google-plus-impact-on-seo.php
So far Google haven't used their +1 data to significantly change ranking of websites but I believe that they will do it sometime soon. But if you would like to get some extra traffic to your website form Google it is strongly recommended to place Google+1 button on your website.
It is Google's first war in the Social Media rampage. It can also be used in the SEO purpose but very limited for now. Maybe later they will design it to have an effect on the ranking as well.