Not a bad post from David.  He has a couple of links from this post talking about advertorials that I don’t get, but this post has some real legs, and the concluding paragraph is actually very good.

The above are probably just the tip of the iceberg. I envision a day where you can search your social network to find and see what products others who you know own -and- whether or not they like them. Moreover, you could learn about the people you don’t know when they recommend a product (which you don’t know now on -traditional- shopping engines). With this information, you could make a more informed buying decision about products you are considering – and keep up to date on the ones you don’t yet know you should be buying. This info would more than just allow individuals to keep up with the Joneses…..

True social commerce would provide consumers with rich social context and relevancy to the purchases which they are making.

Source: Genuine VC: (The Beginnings of) Social Commerce

It touches on the core of the community of interest driven marketspace, vs the brand driven one.