A good way of thinking about the increasing enroachment onto our privacy of firms like Facebook and Google...
"What's happening is that our privacy has become a kind of currency. It's what we use to pay for online services. Google charges nothing for Gmail; instead, it reads your e-mail and sends you advertisements based on keywords in your private messages.
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The genius of Google, Facebook, and others is that they've created services that are so useful or entertaining that people will give up some privacy in order to use them. Now the trick is to get people to give up more—in effect, to keep raising the price of the service."