Very few people realize just how much information their gadgets are constantly leaking out into the world. If you have WiFi turned on, even if you are not explicitly connected to a network - your gadget is constantly scanning looking for WiFi networks to connect to.
In the process - it broadcasts its "MAC Address" (aka "media access control address") - which is essentially a unique serial number that identifies your WiFi device to the network.
Because MAC addresses are unique - an entire industry has emerged around tracking them. Even though a MAC address might not reveal explicitly who you are - a series of scanners could notice that your device went into a women's restroom (female!), shopped in a maternity store (pregnant!), and then lingered window shopping at a chocolate shop (chocohaulic!). This information could be used to target advertising, or worse.
A company in the UK even installed WiFi trackers into downtown recycling bins to gather and log MAC addresses from everyone who wandered by, building up a profile of how people browse the entire downtown area.
Which brings us to a new feature that has just been discovered in the iOS 8 beta that Apple just released -- MAC addresses are now randomized when a device is in scanning mode!
This essentially undermines the entire tracking industry - every few moments an iOS 8 device changes the MAC address it is using, making tracking futile.
Only once you actually log on and connect to a network is your real MAC address revealed.
This is a huge win for privacy, and a huge blow for marketeers tracking and profiling people.