The Web itself is a distributed system but the personal home pages are not really a social network. We can imagine as possible a system where pages/small apps that you host with different cloud (hosting) providers obey the same rules to form together a distributed social network. This way,you have total control on your pages and apps and not a corporation. Is Facebook doomed today or tomorrow? Everything dies in the end but that simple and powerful implementation (idea) capable to replace Facebook can be years away...