Widening Epicenters

Online culture is a fascinating thing. I've talked about it a lot, pointing out individual community behavior, the sizes and lifespans of online communities, community regulation, and community leadership. But now I want to ask a broader question: How has online culture changed over time?

Different question from the center of the Internet or the end of the Internet. (Image source here)

Once upon a time, I once drew a line between "old" and "new" internet culture, with Anonymous as the border between the two. 4chan used to be considered the epicenter of online culture on the Internet. Nowadays, that title might go to Reddit.

But that's just me talking about anecdotes. Can we demonstrate that there is such a thing as online epicenters? Where is it? Where has that title drifted to over the course of the Internet?