The original source of this report appears to be WWDC session 715, "User Privacy on iOS and OS X," presented by Apple Product Security and Privacy representatives David Stites and Katie Skinner.
Whenever you walk around a major Western city with your phone’s Wi-Fi turned on, you are broadcasting your location to government agencies, marketing companies and location analytics firms. At the core of such tracking is the MAC address, a unique identification number tied to each device. Devices looking for a Wi-Fi network send out their MAC address to identify themselves. Apple’s solution, as discovered by a programmer, is for iOS 8, the new operating system for iPhones which will be out later this year, to generate a random MAC addresses while scanning for networks.