I don't have much time to discuss this right now, but I found this article interesting:
It shows that if you put aggregate information about people out there, it can tell you things you don't want to know. The tricky thing is how do you prove that what you are seeing is close enough to a random sample of your population to prove anything.
In any way, in the world of information, it's amazing to see how we can gather data about people. The trick is how this information is going to be used. Can it be the end of illegal porn? Or drugs? I should start searching for "jumping off the bridge" ;-)