Pretty much any device that can connect to the Internet has a unique Media Access Control (MAC) address. These identifiers are part of international connectivity standards that allow us to do simple things like connect an iPhone to Wi-Fi. One problem, though, is that if you have Wi-Fi turned on and you move around a town or city, your device will connect to different public or open Wi-Fi networks as it moves through them. This can allow the NSA or marketing analytics firms to track you using your MAC address and figure out where you like to go.
But Quartz is reporting (via programmer Frederic Jacobs) that Apple's upcoming mobile operating system iOS 8 automatically generates random MAC addresses while iDevices are searching for Wi-Fi networks to join. By making MAC addresses less consistent, Apple is helping to obscure individual identities. That means that it will be harder for marketers to figure out that you're expecting no matter how many baby and maternity stores you go into.
In iOS 7, Apple made a change to keep developers from using MAC addresses for tracking targeted ads or the number of times their app had been downloaded. But the tweak in iOS 8 will have an even broader affect. It's worth noting, though, that even without having a MAC address identifier for your device, companies can still collect personal data from your device if you join their public Wi-Fi. That's one of the big reasons so many stores and restaurants offer it. So don't do anything sensitive while you're on public Wi-Fi, or just turn Wi-Fi off while you're out.