Prior to iOS 8, when you double-clicked your home button you would only see an array of app thumbnails, allowing you to quickly switch between apps. With iOS 8, avatars of your recent and favorite contacts will now show up as well.
The new feature is convenient and one I found myself frequently using, but it's naturally not going to be appreciated by all.
To disable your contacts from displaying in the app switcher, launch the Settings app and select Mail, Contacts, Calendar form the list of options.
Scroll down until you come upon the Contacts section where an option for "Show in App Switcher" can be found. You can disable your recents, favorites, or both from showing up in app switcher with a toggle of a switch.
For more helpful iOS 8 tips, be sure to check out our complete guide to iOS 8.