danah boyd on real names, identity, facebook and google
There is no universal context, no matter how many times geeks want to tell you that you can be one person to everyone at every point. But just because people are doing what it takes to be appropriate in different contexts, to protect their safety, and to make certain that they are not judged out of context, doesn’t mean that everyone is a huckster. Rather, people are responsibly and reasonably responding to the structural conditions of these new media.
Emphasis mine. danah's entire post is worth reading (as always), but I'm always amazed at how this key point is lost in design decisions about social media: context matters. And that's not just about the identity you use when you're in a particular context, but how the things you do in that context get shared across the network. Facebook's working to flatten identity, which is troublesome not only for vulnerable people (as danah points out), but for varied personal expression across the web.