Diffusion vs. concentration

Lorcan Dempsey's blogpost - The Two Ways of Web 2.0 - discusses the diffusion and concentration of Web 2.0. I was particularly struck by his final comments:-
"When we discuss Web 2.0, there is a temptation to think about blogs and wikis, RSS and a Facebook application, and to stop there. There is also some useful thinking about how to expose web services or data in ways that they can be remixed into other applications. However, Web 2.0 is also about concentration, concentration of data, of users and of communications. We need also to think about how libraries reconfigure services in an environment of network level gravitational hubs, driven by network effects. This will involve greater concentration of library resources in various ways, and also - probably? - greater reliance on other web presences to deliver their services. "