As I'm sure you already know, the World Wide Web was invented by a guy called Tim Berners Lee, and I recently came across an interesting interview with him around the social web phenomenon. Here's a short snippet worth taking note of.
"The web has developed from a technological tool, based on technical protocols, to something that also combines social rules.
The internet is based on a series of microscopic rules that combine to affect social behaviour on a macroscopic level, though we do not yet understand how this works.
A site such as eBay is designed and built using protocols such as the mechanisms to identify its users, determine reputations and make payments. However, it is also based on a social system of buying, selling and reputation.
It was designed to work for two people, but because eBay got the microscopic design right, it created a new market that works on a large scale.
Web 2.0 initiatives such as social networking sites have also been technically designed to define the way people talk to each other, but have grown to form macroscopic communities..."
In effect what Berners Lee is saying is that the success of any online enterprise is going to be more and more dependent on understanding the social psychology of audiences on the web. I guess this means understanding the real life motivations and network interactions of the person behind the customer in your target group. For businesses looking to tap into the benefits of Web 2.0 and social networking, it probably means the need to start extending their Persona models to encompass group behaviour rather than just that of the individual.