Deciding on which app has access to private information is the best way to limit the risk of those apps tracking your private data.

Q. How can you check up on what apps are doing with your data?

A. The mail-management service was heavily criticized when a New York Times profile of Uber CEO Travis Kalanick mentioned the ride-hailing company had bought data from showing people’s use of the competing service Lyft.

Users of, which offers to declutter your inbox by identifying the subscriptions you’ve accumulated, then offering one-click unsubscriptions and a daily digest of those you do want, were not amused at the notion that Uber got even an anonymized look at their Lyft ride history.

CEO Jojo Hedaya asked for forgiveness in a blog post. “While we try our best to be open about our business model, recent customer feedback tells me we weren’t explicit enough,” he wrote.

What does—compiles data from a large base of users, strips out personally identifying information like names and addresses, and then extracts patterns from the anonymized remains—is incredibly common in the tech business. For example, Google Maps would be far less useful if it wasn’t informed by anonymized and aggregated data showing which routes were faster or slower.

But (which USA TODAY writers have previously recommended) stands apart from other data-driven services because it needs access to your entire inbox. The travel-management app TripIt  (also covered here) will also make the same request so it can find messages about upcoming travel, but you can also forward those e-mails to the service yourself.

A situation like that requires a high degree of trust in the company involved, which in turn requires transparency from that firm about what it will do with your data. flunks in that regard: Its frequently-asked-questions page doesn’t even try to explain its business model. Its privacy policy discloses the practice (“We may collect, use, transfer, sell, and disclose non-personal information for any purpose”), but Hedaya now admits that’s not good enough.

That’s a common failing in Silicon Valley—I’ve probably seen more than a hundred startup pitches that glossed over how the dot-com would make money—and it invites episodes like this. If a firm can’t tell you upfront how it will earn the income needed to give you a free service (see, for example, Facebook’s explanation of its ad business model), you should look elsewhere.

More often, an app doesn’t ask you to hand over the keys and instead makes a more nuanced request. In Android and iOS, for…