I would say that “necessary” is a strong word. Rather, I view it as just a new model that opens up interesting use cases — ones that were simply not possible before. The “But…why?” link in the further reading section above has my thoughts on this.
I’ve always viewed decentralization as a kind of fractal — there will always be some form of concentration or “clumping” if you will, at some level, as you zoom in or out.
In that sense, decentralization is very close conceptually to oft-misunderstood concepts like “freedom” (of speech, for instance): it is highly specific…