Facebook and Twitter pages are treated like any other pages in our web index so if something occurs on Twitter or occurs on Facebook and we're able to crawl it, then we can return that in our search results. But as far as doing special specific work to sort of say “you have this many followers on Twitter or this many likes on Facebook”, to the best of my knowledge we don't currently have any signals like that in our web search ranking algorithms.
We have to crawl the web in order to find pages on those two web properties and we've had at least one experience where we were blocked from crawling for about a month and a half. And so the idea of doing a lot of special engineering work to try to extract some data from web pages when we might get blocked from being able to crawl those web pages in the future, is something where the engineers would to be a little bit leery about doing that.
So I'm not saying not to use Twitter or Facebook, I love to tweet, there's a ton of people who get a ton of value from both Facebook and Twitter. I think both of those services represent a fantastic avenue, it's a way to drive visitors and traffic to your site, it's a way to let people know about news related to you or your company or website, so I think they're great ways to build up your personal brand. But don't necessarily assume that just because there is a signal on Facebook or Twitter that Google is able to access that. A lot of pages might be blocked or there might be nofollow on links or something along those lines.
There was an SEO that said "OK, we see a lot of links on Facebook and those are the pages that rank well," but that's correlation, that's not causation. Instead it's probably that there's something really awesome and because there is something awesome then it gets a lot of likes on Facebook and a lot of people decide the link to it. That's the sort of thing where the better content you make, the more people are to like it not only in Google but in Twitter and Facebook as well.
...I think over 10 years, we're more likely to understand identity and to understand the social connections between people, but at least for the time being, we have to deal with the web as it is and what we are allowed to crawl and what we can easily extract from that and count on being able to access that in the future.