In February, Facebook purchased the WhatsApp messaging service for the mind-boggling sum of $19 billion. It was the largest acquisition of a venture-backed company ever, but it also proved a clear, albeit subtle, point: Our relationship to personal data is shifting. WhatsApp charges users $0.99 a year, a fee it justifies in a straightforward way—no ads, no data mining, no kidding. Now that one of the world’s most prolific data miners owns WhatsApp, we’ll see if the service can continue to guard privacy in the same way. Regardless, the lesson stands. People  are realizing just how much their data is worth.

Paying for privacy used to be common. Any letter sent via the U.S. Postal Service comes with an implicit security guarantee: Opening someone else’s mail can be a federal offense. Even in the early days of email, an Internet service provider, be it AOL or a local ISP, wouldn’t share customer data without a court order. But then free services arrived—Hotmail and Yahoo in the nineties, then Gmail, Twitter, and others.