However, the big brands now seem to have achieved more prominence, and one that is not always easy to understand from backlinks alone. We touched on this last October in the thread Google's Eric Schmidt Says 'Net Cesspool Needs Brands [webmasterworld.com]. It seemed he was signalling something there - such comments are rarely made lightly.
This thread's title is about "offline" brand authority. No official comments from Google that I've seen - but the idea of giving some trust and authority to unlinked brand citations online seems possible to me.
It's very common to have your brand mentioned without a link in social media than on other types of sites.
I'm sure Google isn't ignoring the boom in social media - I know my clients aren't. Many of them watch the conversations where their brand is mentioned with intensity, and the number of tools for such conversation mining is mushrooming.