Still absolutely excited by the way traffic to http://www.chinasuccessstories.com/ is increasing, I just read a 100% non-Chinese post by SEOmoz that perfectly describes the way I feel about the importance of social communities. For your website ranking, appreciation / valuation and ultimately: traffic.
It complies with what I pointed out in ‘Long live social bookmark exchange’, fully agrees with the added value of sites like Facebook, and underlines the importance of sites like LinkedIn and del.ico.us as described in 'Del.icio.us the China sequel’.
So without wanting to risk dropping too many links here, go ahead and read this: a truly magnificent article on the Basics of Social Media Marketing. -> http://www.seomoz.org/blog/a-visual-tour-through-the-basics-of-social-media-marketing