goodroi - 12:53 pm on Oct 31, 2013 (gmt 0)
To be honest I am not 100% sure about every specific factors that Google is currently using. I have noticed that websites that get a strong boost in social marketing (twitter, facebook, google+, etc.) tend to get a ranking boost.
Is this because Google is tracking tweets or facebook likes? I have doubts that Google is directly doing this since Facebook really does not like Google and would likely try to hamper Google. So maybe this is because Google pays attention to data gathered from Chrome users and could thus identify successful social campaigns. Possibly or maybe this is because that a successful social campaign leads to more brand awareness and thus more people typing your brand name into Google's search box.
It is very hard, if not impossible to completely isolate and identify the specific signals that directly drive rankings. It is much easier to identify signals that have a strong correlation to rankings whether through direct influence, indirect influence or just coincidence.