Jeremy Singer-Vine & Anton Troianovski:

While 7-year-old Eros ViDemantay played with a kid’s app on his father’s phone, tracing an elephant, behind the scenes a startup company backed by Google Inc. GOOG +0.38% was collecting information from the device–including its email address and a list of other apps installed on his phone.
“My jaw dropped,” says Lee ViDemantay, Eros’s father and a fifth-grade teacher at the Los Angeles Unified School District. “Why do they need to know all that?” The app, called “How to Draw–Easy Lessons,” also sent two of the phone’s main ID numbers.
A Wall Street Journal examination of 40 popular and free child-friendly apps on Google’s Android and Apple Inc.’s AAPL +0.70% iOS systems found that nearly half transmitted to other companies a device ID number, a primary tool for tracking users from app to app. Some 70% passed along information about how the app was used, in some cases including the buttons clicked and in what order.
Some three years after the Journal first tested data collection and sharing in smartphone apps–and discovered the majority of apps tested sending details to third parties without users’ awareness–the makers of widely used software continue to gather and profit from people’s personal information.