There's an interesting article at http://www.shirky.com/writings/powerlaw_weblog.html that talks about how consolidation occurs in any on-line community. For his example he used the growing trend of Internet blogging (one such blog: https://www.joeuser.com).

But his data applies to all types of communities that exist on the net. Most people on this site are probably not that familiar with the "history" of skinning let alone the lower level constructs of the "skinning community" but oh boy, there is and it follows much the pattern of other internet trends.

The trend is that in the beginning you start out with a small group of relative equal. But as it grows, consolidation occurs and it starts to fill out a specific geometric pattern in which the top 10% or so of the sites in such a community have 90% of the traffic. Blogs are seeing this and so have customization sites where the top few sites get all the traffic.

Highly recommended reading.