Everything centralized becomes later decentralized repeating the cycle. Often centralization is solution for decentralized schemes and decentralization is often solution for centralisation, in this article borderline is not defined at all. None of them will ever work perfectly without each other. How about internet as one big network? Is the internet centralized or decentralized? It really depends on the view or specific definition/meassure, you could prove both. The same is for bitcoin. Everybody can explain why bitcoin is technically decentralized but few would discuss about social aspect of centralization of ressources and how decentralized bitcoin could (or already is) become centralized.

This is good link (Chapter 2. Decentralization and environmental issues)