Frederic Jacobs (@FredericJacobs) tweeted that iOS 8 randomizes a device's MAC address while scanning for Wi-Fi networks.
Randomized MAC addresses were not demonstrated by Apple during its WWDC keynote address and the new privacy feature (and slide) most likely trickled out during one of the developer sessions.
MacRumors notes that randomizing the MAC addresses of iOS devices when scanning for Wi-Fi networks will make it more difficult for companies to track and gather location data on a customer. Since every iOS device has a unique MAC address it could easily be used for location tracking and data collection via Wi-Fi scanning.
According to the slide, Wi-Fi scanning behavior in iOS 8 "has been changed to use random, locally administered MAC addresses" and said MAC addresses "may not always be the device's real (universal) address." Nice.
Chalk it up as a victory for users concerned about their privacy because iOS 8 devices can't be tracked while doing something as pedestrian as searching for an available Wi-Fi network (which almost every device does).
Mobile marketers that salivate over such device data will undoubtedly be disappointed in Apple's decision, but it's a win for consumers and re-emphasizes Apple's commitment to privacy.