What kind of social marketing are you talking about? The field is rather "wide" to say the least.
You have video blogging on youtube, yahoo video, break, metacafe, veoh, metacafe,,, and other video hosting sites.
You have tweeter and the micro bloggers.
You have myspace and facebook and the other social networking sites.
You have pod casting, and everything that goes along with that.
You have stuff like social bookmarking
The list is almost limitless. When you say Social Marketing, what did you have in mind, or did I miss something in my list?