One problem is that not everything people put on the web is intended to be public for everyone in the world to look at. Especially Facebook is seen as (and used

One problem is that not everything people put on the web is intended to be public for everyone in the world to look at. Especially Facebook is seen as (and used to be) a way to communicate with people you know, not to be stalked by people you don't. It's a mix of broken implicit promises and false (but absolutely natural) expectations. Another, perhaps bigger problem that you seem to have completely missed is that Facebook, Google & Co. don't just collect information about what you put online, but also about what you do online, and can correlate it to a frightening and potentially harmful degree: "Dear Rick, By analyzing your search and websurfing profile we are able to offer you products that are tailored to your personal interests. Included is your personalized catalog: "Kingsize anal dildoes". Christmas is near, and you still haven't found the right presents for some of your family friends and colleagues? No problem! Just send us the name and address of the person you want to surprise with a special present and for only $5 you get a personalized gift catalog tailored to that person's interests! 42 of your acquaintances have already asked us about special presents for you."