Here’s a summary of his key points:
If your facebook profile is completely public, then Google can register the page rank and use it to transfer what I like to call ‘link juice’ to your website. Of course, if your profile isn’t public then Google can’t register the page rank and then this link won’t the same weight and value. It has standard marketing value, but in terms of SEO, you might want to consider opening a public profile specifically for promotional purposes. It’s just a very powerful tool.

Twitter usually adds no-follow to its outgoing links to prevent spamming so its links aren’t as relevant to the SEO cause. Check out his video to learn more on this subject.