Are Social Signals, Useful For Rank Pages?

From many times people said that social media sites play an important role in SEO and also it’s very important to build a brand, to do advertising promotions on social media, and social media relations with fans and customers, but how important is it to Google? Are social signals playing an important part in Google Algorithm and affect rankings?
Google’s head of search, Matt Cutts, published a video answering the question, “are social media sites signals part of the ranking algorithm?” and the short answer was no.
According to Matt Cutts, Google does not give any special treatment to Facebook or Twitter pages. They are, currently, treated like any other sites pages.

Matt Cutts said that “Facebook and Twitter pages are to be dealt with like any other web pages in our web index and therefor if something happens on Twitter or happens on Facebook and we’re able to crawl it, and then we can return that in our search result. But as doing specific work to sort of  this many followers on Twitter or this many likes of Facebook, to the best of my knowledge, Google don’t currently have any signals like that in Google’s web search ranking algorithms.
Matt Cutts explained that they have placed a lot of time into it and at the end twitter and Facebook were blocked for page rank purpose and so work and effort on it were no longer useful.
Matt said that Google did special crawling or indexing for these sites, such as indexing the number of likes or tweets a specific page has but Matt also said that Google does not do that right now.
Google is also worried about crawling identification information at one point and then that details changes, but Google doesn’t see the update until much later and as usual outdated information can be harmful to some people.
Matt also said that he does see Google crawling and indexing and understanding more about identities on the web in the long term.
Matt Cutts says that it is not necessary to assume that Google considers you because just there is a signal on  Facebook or Twitter that Google is able access that.
The reason behind this is that Google has had one experience in which they were blocked from crawling these social sites for about a month and a half and so it’s not worth doing to extract data when they might get blocked again in the future.