From the Washington Post:
It's 3 a.m. Do you know what your iPhone is doing?
Mine has been alarmingly busy. Even though the screen is off and I'm snoring, apps are beaming out lots of information about me to companies I've never heard of. Your iPhone probably is doing the same – and Apple could be doing more to stop it.
On a recent Monday night, a dozen marketing companies, research firms and other personal data guzzlers got reports from my iPhone. At 11:43 p.m., a company called Amplitude learned my phone number, email and exact location. At 3:58 a.m., another called Appboy got a digital fingerprint of my phone. At 6:25 a.m., a tracker called Demdex received a way to identify my phone and sent back a list of other trackers to pair up with.
And all night long, there was some startling behavior by a household name: Yelp. It was receiving a message that included my IP address – once every five minutes.