What's the advantage of open information in the context of social applications? Excluding of course social networks built on mutual interest, like twitter or quora. With real-world friends, family, contacts, etc., the closed nature of facebook is what makes it attractive to me. And I think that's true for most users. It's probably why there's massive outrage every time they relax their privacy defaults.
Maybe data portability? But data on facebook is portable enough, and even if it weren't, what are you going to import it in? Some hypothetical future rival social network? I imagine for a majority of users, simply viewing a friend's profile to remember an email address, phone number, etc, is enough.
I think privacy is actually a good reason for strong data portability. If users can easily leave your service for another, you have a strong incentive not to violate their privacy expectations. To extrapolate that point out: strong data portability and interoperability encourage a competitive environment.
I think you're conflating "closed" with "private." An open social networking environment can still harbor private (I would argue more private) sharing contexts.
From what I understand, it's not an easy process and you can't download important stuff, like your social graph (I think you only get plaintext names, not email addresses, etc.)
Not to mention the graph api. They're very good about giving you all the information you as a user might want (photos, links, messages, wall posts) What it doesn't give you is the kind of data that a competitor might want.
It gives you most of the data you'd be interested in as a user (photos, videos, messages, wall posts). Not so much the data that Google might want, like a easily importable graph. But for everyone else, it's really useful.
Maybe data portability? But data on facebook is portable enough, and even if it weren't, what are you going to import it in? Some hypothetical future rival social network? I imagine for a majority of users, simply viewing a friend's profile to remember an email address, phone number, etc, is enough.