[Schneier on Security] Long news article (alternate source) on iPhone privacy, specifically the enormous amount of data your apps are collecting without your knowledge. A lot of this happens in the middle of the night, when you're probably not otherwise using your phone:IPhone apps I discovered tracking me by passing information to third parties  just while I was asleep  include Microsoft OneDrive, Intuit's Mint, Nike, Spotify, The Washington Post and IBM's the Weather Channel. One app, the crime-alert service Citizen, shared personally identifiable information in violation of its published privacy policy.
And your iPhone doesn't only feed data trackers while you sleep. In a single week, I encountered over 5,400 trackers, mostly in apps, not including the incessant Yelp traffic.