For years now, people have been letting Unroll.me read the contents of their email inboxes, to help them unsubscribe from email spam. The service was endorsed by our sister site Lifehacker in 2011 for its effectiveness in finding and cleaning out unwanted subscriptions (and Gizmodo wrote about its iOS app release last year).

But a New York Times profile of Uber this weekend revealed, in passing, that Unroll.me, which is owned by a company called Slice Intelligence, isn't just in the business of tidying up customers' inboxes. Slice makes money by scanning its users' email for receipts, then packaging that information into intel reports on consumer habits. Uber, for example, was paying Slice to find users' Lyft receipts, so it could see how much they were spending each month, "as a proxy for the health of Lyft's business."