From a new Wall Street Journal analysis by Julia Angwin and Jeremy Singer-Vine of the data-devouring properties of apps, which are often free and almost always come with a cost:

“Not so long ago, there was a familiar product called software. It was sold in stores, in shrink-wrapped boxes. When you bought it, all that you gave away was your credit card number or a stack of bills.

Now there are ‘apps’—stylish, discrete chunks of software that live online or in your smartphone. To ‘buy’ an app, all you have to do is click a button. Sometimes they cost a few dollars, but many apps are free, at least in monetary terms. You often pay in another way. Apps are gateways, and when you buy an app, there is a strong chance that you are supplying its developers with one of the most coveted commodities in today’s economy: personal data.

Some of the most widely used apps on Facebook—the games, quizzes and sharing services that define the social-networking site and give it such appeal—are gathering volumes of personal information.

A Wall Street Journal examination of 100 of the most popular Facebook apps found that some seek the email addresses, current location and sexual preference, among other details, not only of app users but also of their Facebook friends.”