The first Matt Cutts Answers Questions About Google video of the year has been posted, and in it Matt addresses links from Twitter and Facebook, after talking about his shaved head again. Specifically, the submitted question he answers is:
Links from relevant and important sites have always been a great way to get traffic & acceptance for a website. How do you rate links from new platforms like Twitter, FB to a website?
Essentially, Matt says Google treats links the same whether they are from Facebook or Twitter, as they would if they were from any other site. It's just an extension of the pagerank formula, where its not the amount of links, but how reputable those links are (the company uses a similar strategy for ranking Tweets themselves in real-time search).
"At least in our web search (our organic rankings), we treat links the same from Twitter or Facebook or, you know, pick your favorite platform or website, just like we'd treat links from Wordpress or .edus or.govs or anything like that," says Cutts. "It's not like a link from an .edu automatically carries more weight or a link from a .gov automatically carries more weight. But, the specific platforms might have issues, whether it's not being crawled or it might be nofollow. It would keep those particular links from flowing pagerank."
There you have it. Matt's response probably doesn't come as much of a surprise to most of you, but it's always nice to hear information like this straight from Google.