It is super annoying. Many apps "Google apps I am looking at you" I accidentally press the back button and it just stupidly closes the app. I hate this because then I have to relaunch it draining the battery if it a app that is bloated and takes a while to load. Just get rid of the back button and add a back arrow like on iOS. So much easier. What is the big deal as you can still go into the multitask and close the app that way.