I think you could operate some sort of peer-to-peer network, but a lot of them still require domain registration to provide individual domain addresses. A domain is like a network of many machines. IPV6 is able to give every machine ever made and, I think, any machine ever to be made in the future an individual address, but these are machine specific and not network specific. This is why there is the Domain Name Address system ( I am forgetting the exact name for it). Domains are for separate networks