The notions of privacy being advanced here seem overly simple to me. Certainly, in terms of information technology, information that is not private is essentially public in that it can be instantly distributed at no cost to an unbounded number of people. But in the social world the notion of privacy is more nuanced: it's not all or nothing, and even if it were information would not switch from being completely private to totally public in an instant. A friend may tell me something about themselves that I will not pass on to others. Often I will exercise that discretion even though not explicitly requested, because it is 'obvious' (to me) what my friend would want. Such decisions contribute to the growth and strengthening (or not) of relationships. In other cases I may choose to pass on information to one friend but not another, again for similar reasons. Now it is true, in all of these cases, that depending on the discretion etc of those who are told, the information may gradually propagate throughout the 'social network.' But social propagation is quite different from the instantaneous broadcasting of information that Facebook is doing. The social propagation is slower, and each step of the propagation is associated with a particular person and may also be accompanied by additional information provided by that person. Being socially sophisticated creatures, we also understand that if information has traveled through more than a few people, it is likely to have morphed. And finally, anyone who plays a role in this sort of information propagation is gaining something from it -- perhaps establishing/strengthening their identities (I'm in the know), perhaps strengthening relationships (here's some hot gossip, just for you my friend). All of this gives the social propagation of information a very different character from its digital analog, which, I suggest, makes it feel much more comfortable. But in Facebook people are posting their information for anyone to read! True, but that brings us to the front lawn analogy. While in theory I can't control who drives by my front lawn, in practice I do have some control. I can select where I live (assuming economic means), and that in turn has a bearing on the numbers and types of people who drive by. In theory, anyone can drive by, but in practice the numbers and types of people are quite stable. I don't usually go out of very far out of my way on a drive to work or trip to the store. Driving around the city has a cost structure that we count on when selecting a living place, and likewise seeking information has a cost structure that we count on when posting information for others to read. Facebook has just radically changed that cost structure, and given that most people relate to the social notion of privacy rather than the information technology notion, that provokes notice. While we might call users naive for not understanding how 'privacy' works on the internet, we might also call the designers behind Facebook naive for not understanding how privacy works in the social world. -- ------------------------------------------ Tom Erickson IBM T.J. Watson Research Center Email: snowfall@acm.org (preferred); snowfall@us.ibm.com(IBM confidential) http://www.visi.com/~snowfall/