It won't shock you to hear that Android apps send a lot of data, but you may be surprised at how much of it isn't really necessary... or public, for that matter. MIT researchers have determined that "much" of the hidden data sent and received by the 500 most popular Android apps isn't necessary to the functionality. For example, a Walmart app talks to eBay whenever you scan a barcode -- there's no practical difference when you sever that connection. Out of the 47 apps that MIT modified to prove its case, 30 were virtually indistinguishable from the official versions. The rest only had minor issues, like missing ads.