If an Appleseed node turns evil, they'll probably take the data of, maybe, 100,000 or a million users with them. When Facebook turns evil (some would say saying "when" isn't necessary), 500 million people's data goes down.
One of the things that's kept Facebook free of social pressure in terms of acting evil, is that the walled garden approach means that people can't leave without losing their social network. Appleseed (and distributed social networking) at least provides a certain competition, because if a node acts up, users can leave that node, go to another node, and reconnect with their friends. It won't be totally painless (at first anyways), but that's pressure that Facebook simply does not feel at this point, and that has a very negative effect on it's behavior.
The question is: how many people would prefer this more email-like system?
I'll be the first to admit that a centralized system holds advantages over a decentralized one (and vice versa). A lot of these issues, we may not even know the full extent of until we see heavy use. This is pretty new territory, and I'm open to any suggestions.
It's the big reason why I rewrote Appleseed to be extremely flexible, to use pervasive hooks and an MVC model, and to be protocol agnostic. Also, why Appleseed has one-click server upgrades and other ease-of-administration features.
There's some really solid work being done on protocol development, but I think we all need to be honest that the first steps out of the gate are gonna be rocky. Hopefully Appleseed can adapt quickly enough until distributed social networking matures.
Ah, but this is pretty much an illusion on Facebook too, even if it is an expectation (remember the FB employee interview a bit ago where they mentioned saving EVERYTHING - which is plausibly more than what webmail does). You could have an interface that seemed to take back content if it made people feel better but it's ultimately bullshit.
My theory is that as people use the web, they'll begin to understand that sharing has it's inherent costs and no one is going to be able to protect you from them. In that way then, a more email-like service will make more sense to people.
The remaining question I have is: while the feed provides a link/summary, what's preventing a node from following that link and then caching/storing that data?
You've come up with a nice way of propagating block lists and kudos for addressing the problem. However, with Facebook, I only have to worry about Facebook behaving badly. I don't have to worry about multiple companies and different bad behavior.
Plus, sometimes bad behavior can become public much later. Let's say that I operate Applebook. I'm running a nice Appleseed server that has some users. I decide to start storing the data from other nodes. Maybe I'm even doing it for practical reasons like performance or as a service to my users. Then 5 years down the line, my fortunes take a turn for the worse. I decide to go evil! Sure, maybe the second I turn evil it gets propagated out fast and I can't get access to any future data. However, I still have all that past data!
And this is a concern with Facebook as well. They could turn evil some day and betray us all. However, it's one company to worry about rather than dozens or more.
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Also, as an aside, sometimes the summaries might contain the information people want deleted. If you have a 140 character status update Twitter-style, there isn't much of a summary to be made.
Right now, we're used to being allowed to remove things from social networks. Unlike email, it's communication that we can take back. Wall posts, status updates, photos, etc. can be deleted. If I email you a photo, it's always there for you. In some ways, a distributed social network is more like email. Once you've sent it out to your friends, it can't really be taken back. That's very different from Facebook. With Facebook, users expect to be able to remove content at any time and it's inaccessible to other users (unless they decided to copy/paste or save it in another way).
The question is: how many people would prefer this more email-like system? The advantage is that one wouldn't be beholden to a central service like Facebook or Twitter. Users have been skittish about privacy anytime Facebook changes something. How much of that is posturing and how much of it is users who would discontinue using it if they thought they couldn't remove things from the view of others?