Perfect framing can make or break a photo. Take that green screen photo from #10 for example. A little bit of cropping on the sides of that photo may have fooled a few more people into thinking it was real. In the case of this picture, the tight cropping gives it a feeling like this slackliner is floating in thin air. Not knowing where he's going or where he came from gives a sense of magic. It makes the feat seem unbelievable. With that city in the deep distance I'm completely mesmerized.
Even given the reality of the situation, it's still unbelievable when you consider its someone walking on a rope across a huge distance. Slacklining should totally be an olympic sport. It takes such an incredible amount of strength. More than curling at least. That's just people sweeping.