There are plenty of things you and I don't want anyone to know. I don't want the world to know when I'm on vacation. I don't want my neighbors to know I left my balcony door open and I just have the screen door closed so I conserve energy. I don't want every girl I meet to know that I collect comic books. The idea that I shouldn't be doing any of those things is completely absurd.
In the same fashion, would you like everyone to know what parking spot your teenage daughter parked in, in the back of a mall parking lot Friday night? Or where your kids go to daycare? (hypothetical, I don't have kids but you bet I'd be concerned about them using foursquare) Could we change Eric Schmidt's quote to, "If your kids are doing something you don't want everyone to know, may be they shouldn't be doing it in the first place?" I don't think so. Your kids aren't that much different than your 60 year old mother or 70 year old dad. That is a lot of people.
It was hardly 10 years ago that the message was - never meet anyone you first met online. What happened to that? Now the message is, share all your personal private information with the entire world, you have nothing to worry about. We are Facebook/Google and these features are amazing. That is a lie.
Perhaps the parallel increase in information access by law enforcement has made us feel safer. The same technology criminals use to exploit us is used to track them. When something bad happens to someone we know more about what happened, quicker. While this may be an acceptable trade off in a first world country I do not believe the same applies in one such as Mexico.
Yeah online privacy is nearly non existent. Especially so when you are reckless and use connected identity systems. That doesn't mean the message should be "give up." That is the message Google and Facebook's PR machines are sending because they can make a lot more money from advertising when they do it.
As soon as hacker news switches to facebook's commenting system or any other public id, I'll never make another post here again. I have left communities I've been active in because of this. The message to our friends and family, and if we own businesses, the world, should be stop sharing all of this information publicly. There is no reason to. Its not safe for you and its not safe for your family.