Auto focus can be a really mean thing. Just when you want to focus on something, it will lose focus and will start focusing on another thing. This is a phenomenon that anyone with a camera would relate to and would mention as the truth. However, you seriously need to have crappy luck to have auto focus choose a horse's arse over your face. This guy wanted auto focus to focus on his face, but that didn't happen.
While you should be careful with choosing the right background while taking a picture, it is also advised that you not trust auto focus when it comes to focusing on you. Auto focus can be really confusing, and it is hence recommended that you just change backgrounds to avoid the fate this guy brutally suffered from.