According to
Social Times,
Marketing Times, and
Search Engine Land, Google and Bing have both confirmed that links shared on both Twitter and Facebook do in fact affect search engine results. This has been a question that has not been definitely answered until now, and yet it still seems rather murky as to how the link sharing actually does affect the results. Google stated that it uses something called Author Authority to gage the SEO ranking of sites and Bing uses a similar metric called Social Authority. Both of these are based off of a Twitter user's "author quality". The reason they can't use this same metric with Facebook is because they do not have acces to personal information on profile walls within Facebook.
