It has been long clear that blogs and other kinds of fast-updating media – especially of the text-rich variety have dominated other websites in search.
The formula is pretty simple: New content is news, blogs and public social media produce more new content than even periodicals, therefore to the search engine they essentially produce more news. A standard method of ranking includes a measure of relevance – which for many things will be how recently the information was acquired. The search engine can’t tell Plato from Gawker and add to that a frequency of smaller and more diverse postings (as in Twitter or Facebook,) and you have a recipe for search-domination.
Jennifer Van Grove at Mashable writes:
Essentially what customers, fans, and detractors are posting to social media sites are dominating the brand name search experience over social media content created by the brands themselves. This data clearly creates a legitimate reason for brands to be proactive with their social media presence, as participating in the exchange about their brand should improve the quantity and quality of customer-created social media content that searchers will happen upon.
It is worth noting that this only effects opinion and brand, since these sites (blogs and the like) are less apt to drive sales than product-rich websites. They have a broad but shallow impact. It really makes clear what marketers have been saying about word-of-mouth advertising for a long time, doesn’t it?

Google Social Search is coming!
Add to this the emergence – and how soon no-one knows for sure – of Google Social Search, it might just be the moment to be on social media (or the time to stay very, very far away from it!) Which you choose depends on how you interact with customers.
A final note is that Google Social Search requires a person to keep connections in their Google account (which not everyone has or does) so the impact may be spotty for awhile. I’ve experimented myself, and my results tend to be dominated by a few people who are more connected in that way, or who run blogs or comment on blogs frequently.
It is cool, though, in a weird kind of way. What kind of SEO can you do on that kind of stuff?
My brain replies:
To: john
Subject: your posting on Yelp!
Body: Can you please include the words ‘diamond retail experience‘ in your review? Thanks.
Oh! That would be strange.