Google is about to release it's Facebook Like Button competitor, the “+1” button. In an effort to compete against Facebook's famous like button, Google is using it's might in online data acquisition to integrate the button into it's organic search results. This will go a long way to integrate seo with social media and referrals.
It has been long known that Google places a lot of emphasis on backlinks, or ‘Votes' for websites. The more ‘votes' you have from other sources on the internet, the more important your site is perceived and your rankings for keywords on your site or what your site is about, elevates you within the search engines. Integrate that with a referral ‘vote', and you can have a powerful tool in google placement.
Needless to say, the battle between the big boys of the internet is heating up.
The article to which I refer to in the video is here.