This sort of decentralization is probably possible, following a Gnutella-like model, but I suspect the limiting problem will be searchability of the fluctuating network topology. You can combat that, of course, by enlisting some sort of search engine, but then you've just centralized again, defeating your entire purpose.

I think there have been various projects to design a decentralized, censorship-resistant network (FreeNet, I think, is one example?). Obviously though, they have not caught on as bulwark elements of the internet - there must be some significant drawbacks.