Why does a MacBook Pro keep dialing in its location through Find My Mac after a clean install?
Here's what Apple says:


  Because of how Find My Mac works, you must deselect the box next to Find My Mac in the OS X System Preferences > iCloud pane to remove your device from your iCloud Find My iPhone, iPad, iPod Touch, or Mac device list.


One of the ways this persistence is implemented is by writing a Find My Mac token to NVRAM, the persistent memory in Intel Macs. You can see this token by running the following command in a terminal:

nvram -p | grep fmm


On my Mac, the result includes my name, Apple ID, and the name I gave the computer, along with some encoded information that probably includes a key of some sort.