Do you have AT&T? Most iPhone and iPad devices are linked to it. If you're one of them, you should be aware that AT&T is selling your information. But you can change that. Just opt out.
Here's the kind of information AT&T will be selling: your location based on WiFi networks you connect to, Web browsing data, and apps you use. So if you're uncomfortable with that, how do you opt out?
Just log into your AT&T account on this site and change your settings to say you don't want your data used for external marketing and analytics reports.
Consider yourself warned... Control your privacy. Stop unwanted spying -- at least for now.