It just occurred to me how different activities on Social Networks can reveal the data that is protected by the privacy policy. For example I tend to keep my birthday private, but still the birthday wishes on my wall reveal the exact data of my birthday to all of those that I tried to hide it from. I am sure there is some research that deals with such dangers in more details.

I am thinking about a framework for consequences: that would, in case you set:

show birthday: only to me.
show wall: to my friends.

tell you:

If some of your friends wish you a happy birthday, the others will know it.

Is it possible that a bit of Expert Systems can make some use here? Is the Semantic Web the solution. Or should we just make everything public and don’t worry about it?