I also think it's important to realize that social factors extend FAR beyond Twitter, Facebook and LinkedIn. Social media listening tools exist that monitor over 10 million domains - I know this number quite well because I've helped to develop these tools and use them in my professional work.
Every blog and news article that allows comments is a social medium. Every forum is a social medium. YouTube pages are a kind of social media. There are many formats out there if Twitter isn't your particular cup of tea.
It is very hard to publish something of value on teh web and avoid all social mention - although it can be done if you go into old school mode, if you never really got The Cluetrain Manifesto message. To me, using social factors as part of the ranking algorithm makes a TON of sense. After all, if search engines don't actually reflect the public interest, they'll go out of business.
I also appreciate viggen's observations very much. Social media are a great leveler. Even the "grsat" are socially available as never before. I recently made contact with a world class particle physicist via Twitter.
There is an entire human race, and a significant portion of it is being social online. It can be a great pleasure to get involved. It can benefit your own web publishing to get the feedback that comes naturally to those who are socially engaged.