Google's update to its more "social" search experience covers different areas. First, social results will now be mixed throughout search results based on their relevance - meaning relevance to the user conducting the query and of course the content shared by those in the users social graph - as indicated to Google through the use of connecting accounts on the users public Google profile.
Social search results were formerly available at the bottom of the search results page but now they can (and do) appear anywhere and include an annotation about the source referring or "recommending" that content.
Google has also made social search more comprehensive by finally including some of that Twitter firehose it paid to access back in the summer of 2010. Users will now see notes for links people have shared on Twitter and other sites. (We're still looking into what other sites.) Again, if someone is connected to you publicly and shares a link, the chances are good you might see it when searching at Google.
While it will certainly be interesting to see how this pans out - particularly users reactions, the more important question, and the one you should be asking is, "Why am I not out building more social relationships?"