>Diaspora apparently requires you to run your own set of web hosting services in preserve your privacy, which no one really cares about
To me, this reads the same as "having an email address requires you to run your own email server". If Diaspora takes off, I'm sure it will be another check-box on ISP features lists.
I think the idea of a Balkanised Facebook is a good one, esp. if was business related. Keeping in touch with customers and aligned groups in a relaxed place but without the threat of one of your personal friends posting pictures of what you did on your drunken weekend away.
Great services like Gmail only became possible because SMTP isn't tied to a particular proprietary service. Individuals can use the service that's most appropriate for them. For some people, that's Outlook, for others, a webmail provider. Competition works.
What we really need is a system that crosses social-networking-service providers in the same way that SMTP broke down the barriers between various mail systems.