Aleks raises some very interesting points by positioning eBay as an autonomous nation. At first glance, I would go so far as to say that the individual proof points do warrant more than their fair share of merit. From the social feedback system to the economic structure through PayPal, one can see how easy it is to make the leap. As one can also see however, from the resulting comments provided by @petehindle, @cyberissues and @TimFootman, upon further scrutiny the analogies end almost as quickly as they begin.
It is Aleks’ reference to eBay’s “development of smaller sub-communities” that I’d like to delve a little deeper into. At its core, eBay is one of the first (if not the first if you exclude email) social networks; connecting people with similar interests and applying online commerce to that direct connection. Ironically, in a world that has seen us move away from knowing our milkman, butcher, or postman and turned us into a self-serving society of faceless convenience, eBay - or rather the eBay community - has succeeded due in large part to the continued fact that people do want that individual connection.
This leads me to an interesting opportunity (or challenge depending on your viewpoint) currently being faced by eBay as we embrace the Digital Revolution.