Tim- excellent and provaocative post. At the end of the day, if social software is not about people and identity, then it will fail. We at ThisNext have spent a lot of time thinking about what makes for successful social software, how it applies to commerce, the politics of identity, and consumer psychology.
I posted a longer response on my blog: http://gordon.blogsmith.com/2006/08/29/identity... look forward to evolving our collective understanding of what will make for successful identity expression in commerce.