iOS 8 is packed with great new features, and an updated private browsing mode is one of them. As Redditor ILiketoSpooner points out, private browsing mode is not really as conveniently private as it used to be.
In iOS 7, when you left private browsing mode you would see a prompt to close all your open tabs. Now, there is no prompt and when you leave private browsing mode all your tabs are left wide open for the world to see. So, if someone opens up Safari on your phone they can switch over to private browsing and see everything you had open. If you don't want anyone seeing what you were checking out last, you have to individually close each tab.