If you are an Android OS user think again about the apps you use. At last months FTCs PrivacyCon researchers showed how more than 1,325 (out of 88,000) apps on the Google Play store effectively ignored the OS permission model and created side and covert channels that exfiltrated data from a user device. Lots of good technical details are in their paper:"50 Ways to Leak Your Data: An Exploration of Apps’ Circumvention of the Android Permissions System"
