As of today google will be taking into account the "Social Media Status" of a web page to determine it's ranking. A nice summary can be found in this telegraph article: google updates social search.
One development is that social media sites can now be listed in google search results, but this needs to be enabled by the user in their google settings provided that they are logged in. The interesting thing from my perspective is that it looks like the Page Rank algorithm has been updated to take into account how social media websites see webpages.
So what does this mean? Let's focus on facebook for now... It essentiall means that the ammount of 'likes' that your web pages has could have a serious effect on how your page is ranked. Could lots of page 'likes' be the new holy grail of getting your website onto the google top-spot? The reality of the matter is that Google is not stupid, and like the traditional pagerank algorithm they will have processes in place to prevent spam. It is a sensible decision really, page 'likes' are generally more measurable and reliable as a genuine account needs to log in to like a particular page.
The main concern with this new page rank system is that spammers could sign up to mass social media accounts just to push up the page likes of a page. If google can somehow rank the quality of each and every page 'like' and base the pages ranking on the quality of it's 'likes' then it will be much more robust.
Either way, it is certainly worthwhile putting social media shares and facebook like buttons onto pages as part of any search engine optimisation strategy. See that like button on the right of this page? It would be very kind of you if you could click it!