Matt Cutts has put an end to the speculations of Google using Facebook and Twitter signals to rank pages.
Answering to the question "are Facebook and Twitter signals part of the ranking algorithm?" in the video, Cutts said that Google doesn't not give special treatment to Twitter or Facebook pages. These are in fact at present treated like any other page.
Cutts also said that Google does not do special indexing or crawling for these sites, such as the tweets a specific page has or indexing the number of likes. He told that Google had put a lot of engineering time into special crawling of these sites earlier, but these were blocked & Google decided not to waste efforts anymore.
Google is also considering the outdated information factor while crawling the identity information. If the information changes at one point of time and Google doesn't see the update for a long time, it could be harmful to some people.
Matt Cutts said that he does consider Google indexing, crawling, and understanding as more about identities in the long term on the web.Google Doesn't Consider Using Facebook or Twitter Social Signals to Rank Pages!,