Michael Chisari of the Appleseed Project: 1. Data privacy itself is easily achieved, we have decades of experience and precedence in how to secure data, but adding human relationships and trust complicates it exponentially. In distributed social networks, you have questions of identity, trust, claims, relationship, that you often don't have in centralized networks, let alone in systems where an administrator makes the decisions from the top down. And the problems of privacy and trust are as much social problems as they are technological ones, and we often look to technological solutions to solve these social problems. 2. Technology can't solve social problems, however. No algorithm can ever predict that Bob would feel scorned by Alice, and use his position of trust to share her photos outside of her accepted circle. But we can create tools which aid social solutions to technological problems. 3. Privacy is the most obvious concern, and the issues that exist today with privacy are more user-facing than anything. Facebook's approach to privacy is not always terrible, they have friend categorization and access control, much like Appleseed or other privacy-centric solutions. But their user interface for managing them is particularly dense and poorly designed (some might argue purposely so). A feature isn't worth anything if nobody uses it, and a powerful privacy user interface is an example of technology aiding the user to solve social problems of trust, instead of trying to make the decisions for them. 4. These questions come down to the most important aspect of the social web: The interface is the killer app, not the engine. Your underlying code can be the most private, secure, encrypted, etc. code ever written, but if the user interface fails to explain and urge the lowest common denominator to use those features, then often, the rest of the social web follows suit. The biggest challenge the open source community has is only partly a technological one, but mostly a social one. The user interfaces we build will determine whether users of the social web can have a reasonable expectation of privacy, or whether they continue to operate in a panopticon ever without realizing it.