It is a federal crime to open a piece of junk mail that’s addressed to someone else. Listening to someone else’s phone call without a court order can also be a federal crime.

The Supreme Court has ruled that the location data served up by mobile phones is also covered by constitutional protections. The government can’t request it without a warrant.

But the private sector doesn’t need a warrant to get hold of your data. There’s little to prevent companies from tracking the precise movements of hundreds of millions of Americans and selling copies of that dataset to anyone who can pay the price.