Bruce Schneier recently blogged about his A Taxonomy of Social Networking Data essay in the IEEE Security & Privacy magazine. There are six categories of data: Service, Disclosed, Entrusted, Incidental, Behavioral, and Derived.

It’s also clear that users should have different rights with respect to each data type. We should be allowed to export, change, and delete disclosed data, even if the social networking sites don’t want us to. It’s less clear what rights we have for entrusted data — and far less clear for incidental data. If you post pictures from a party with me in them, can I demand you remove those pictures — or at least blur out my face? (Go look up the conviction of three Google executives in Italian court over a YouTube video.) And what about behavioral data? It’s frequently a critical part of a social networking site’s business model. We often don’t mind if a site uses it to target advertisements, but are less sanguine when it sells data to third parties.